diff --git a/CMakeLists.txt b/CMakeLists.txt
index bb91cf8b6d6..d9cab119d93 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14169,6 +14169,7 @@ add_executable(interop_server
   ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_load_report.grpc.pb.cc
   ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_load_report.pb.h
   ${_gRPC_PROTO_GENS_DIR}/src/proto/grpc/testing/xds/v3/orca_load_report.grpc.pb.h
+  src/cpp/server/orca/orca_service.cc
   test/cpp/interop/interop_server.cc
   test/cpp/interop/interop_server_bootstrap.cc
   test/cpp/interop/server_helper.cc
diff --git a/build_autogenerated.yaml b/build_autogenerated.yaml
index 744fd06f252..7d93f037654 100644
--- a/build_autogenerated.yaml
+++ b/build_autogenerated.yaml
@@ -8988,6 +8988,7 @@ targets:
   - src/proto/grpc/testing/messages.proto
   - src/proto/grpc/testing/test.proto
   - src/proto/grpc/testing/xds/v3/orca_load_report.proto
+  - src/cpp/server/orca/orca_service.cc
   - test/cpp/interop/interop_server.cc
   - test/cpp/interop/interop_server_bootstrap.cc
   - test/cpp/interop/server_helper.cc
diff --git a/src/proto/grpc/testing/messages.proto b/src/proto/grpc/testing/messages.proto
index ed7f8ead793..921e8bf0d41 100644
--- a/src/proto/grpc/testing/messages.proto
+++ b/src/proto/grpc/testing/messages.proto
@@ -177,6 +177,9 @@ message StreamingOutputCallRequest {
 
   // Whether server should return a given status
   EchoStatus response_status = 7;
+
+  // ORCA data to be returned out of band
+  xds.data.orca.v3.OrcaLoadReport orca_oob_report = 8;
 }
 
 // Server-streaming response, as configured by the request and parameters.
diff --git a/test/cpp/interop/BUILD b/test/cpp/interop/BUILD
index 7b64a4e7ac9..6178cdab986 100644
--- a/test/cpp/interop/BUILD
+++ b/test/cpp/interop/BUILD
@@ -83,6 +83,7 @@ grpc_cc_library(
     language = "C++",
     deps = [
         ":server_helper_lib",
+        "//:grpcpp_orca_service",
         "//src/proto/grpc/testing:empty_proto",
         "//src/proto/grpc/testing:messages_proto",
         "//src/proto/grpc/testing:test_proto",
diff --git a/test/cpp/interop/backend_metrics_lb_policy.cc b/test/cpp/interop/backend_metrics_lb_policy.cc
index 93eb7caf43b..5a3eb1dbbab 100644
--- a/test/cpp/interop/backend_metrics_lb_policy.cc
+++ b/test/cpp/interop/backend_metrics_lb_policy.cc
@@ -20,6 +20,9 @@
 
 #include "test/cpp/interop/backend_metrics_lb_policy.h"
 
+#include "absl/strings/str_format.h"
+
+#include "src/core/ext/filters/client_channel/lb_policy/oob_backend_metric.h"
 #include "src/core/lib/iomgr/pollset_set.h"
 
 namespace grpc {
@@ -115,6 +118,20 @@ class BackendMetricsLbPolicy : public LoadBalancingPolicy {
     LoadReportTracker* load_report_tracker_;
   };
 
+  class OobMetricWatcher : public grpc_core::OobBackendMetricWatcher {
+   public:
+    explicit OobMetricWatcher(LoadReportTracker* load_report_tracker)
+        : load_report_tracker_(load_report_tracker) {}
+
+   private:
+    void OnBackendMetricReport(
+        const grpc_core::BackendMetricData& backend_metric_data) override {
+      load_report_tracker_->RecordOobLoadReport(backend_metric_data);
+    }
+
+    LoadReportTracker* load_report_tracker_;
+  };
+
   class Helper : public ChannelControlHelper {
    public:
     explicit Helper(RefCountedPtr<BackendMetricsLbPolicy> parent)
@@ -123,8 +140,12 @@ class BackendMetricsLbPolicy : public LoadBalancingPolicy {
     RefCountedPtr<grpc_core::SubchannelInterface> CreateSubchannel(
         grpc_core::ServerAddress address,
         const grpc_core::ChannelArgs& args) override {
-      return parent_->channel_control_helper()->CreateSubchannel(
+      auto subchannel = parent_->channel_control_helper()->CreateSubchannel(
           std::move(address), args);
+      subchannel->AddDataWatcher(MakeOobBackendMetricWatcher(
+          grpc_core::Duration::Seconds(1),
+          std::make_unique<OobMetricWatcher>(parent_->load_report_tracker_)));
+      return subchannel;
     }
 
     void UpdateState(grpc_connectivity_state state, const absl::Status& status,
@@ -216,14 +237,21 @@ void RegisterBackendMetricsLbPolicy(CoreConfiguration::Builder* builder) {
 
 void LoadReportTracker::RecordPerRpcLoadReport(
     const grpc_core::BackendMetricData* backend_metric_data) {
-  absl::MutexLock lock(&per_rpc_load_reports_mu_);
+  absl::MutexLock lock(&load_reports_mu_);
   per_rpc_load_reports_.emplace_back(
       BackendMetricDataToOrcaLoadReport(backend_metric_data));
 }
 
+void LoadReportTracker::RecordOobLoadReport(
+    const grpc_core::BackendMetricData& oob_metric_data) {
+  absl::MutexLock lock(&load_reports_mu_);
+  oob_load_reports_.emplace_back(
+      *BackendMetricDataToOrcaLoadReport(&oob_metric_data));
+}
+
 absl::optional<LoadReportTracker::LoadReportEntry>
 LoadReportTracker::GetNextLoadReport() {
-  absl::MutexLock lock(&per_rpc_load_reports_mu_);
+  absl::MutexLock lock(&load_reports_mu_);
   if (per_rpc_load_reports_.empty()) {
     return absl::nullopt;
   }
@@ -232,9 +260,34 @@ LoadReportTracker::GetNextLoadReport() {
   return report;
 }
 
+LoadReportTracker::LoadReportEntry LoadReportTracker::WaitForOobLoadReport(
+    const std::function<bool(const xds::data::orca::v3::OrcaLoadReport&)>&
+        predicate,
+    absl::Duration poll_timeout, size_t max_attempts) {
+  absl::MutexLock lock(&load_reports_mu_);
+  // This condition will be called under lock
+  auto condition = [&]() ABSL_NO_THREAD_SAFETY_ANALYSIS {
+    return !oob_load_reports_.empty();
+  };
+  for (size_t i = 0; i < max_attempts; i++) {
+    if (!load_reports_mu_.AwaitWithTimeout(absl::Condition(&condition),
+                                           poll_timeout)) {
+      return absl::nullopt;
+    }
+    auto report = std::move(oob_load_reports_.front());
+    oob_load_reports_.pop_front();
+    if (predicate(report)) {
+      gpr_log(GPR_DEBUG, "Report #%" PRIuPTR " matched", i + 1);
+      return report;
+    }
+  }
+  return absl::nullopt;
+}
+
 void LoadReportTracker::ResetCollectedLoadReports() {
-  absl::MutexLock lock(&per_rpc_load_reports_mu_);
+  absl::MutexLock lock(&load_reports_mu_);
   per_rpc_load_reports_.clear();
+  oob_load_reports_.clear();
 }
 
 ChannelArguments LoadReportTracker::GetChannelArguments() {
diff --git a/test/cpp/interop/backend_metrics_lb_policy.h b/test/cpp/interop/backend_metrics_lb_policy.h
index 9853f3279a1..cf0f1618b67 100644
--- a/test/cpp/interop/backend_metrics_lb_policy.h
+++ b/test/cpp/interop/backend_metrics_lb_policy.h
@@ -37,13 +37,20 @@ class LoadReportTracker {
   void ResetCollectedLoadReports();
   void RecordPerRpcLoadReport(
       const grpc_core::BackendMetricData* backend_metric_data);
-  // Returns the next load report, or nullopt if the queue is empty.
+  void RecordOobLoadReport(const grpc_core::BackendMetricData& oob_metric_data);
+  // Returns the next per-RPC load report, or nullopt if the queue is empty.
   absl::optional<LoadReportEntry> GetNextLoadReport();
+  LoadReportEntry WaitForOobLoadReport(
+      const std::function<bool(const xds::data::orca::v3::OrcaLoadReport&)>&
+          predicate,
+      absl::Duration poll_timeout, size_t max_attempts);
 
  private:
   std::deque<LoadReportEntry> per_rpc_load_reports_
-      ABSL_GUARDED_BY(per_rpc_load_reports_mu_);
-  absl::Mutex per_rpc_load_reports_mu_;
+      ABSL_GUARDED_BY(load_reports_mu_);
+  std::deque<xds::data::orca::v3::OrcaLoadReport> oob_load_reports_
+      ABSL_GUARDED_BY(load_reports_mu_);
+  absl::Mutex load_reports_mu_;
 };
 
 void RegisterBackendMetricsLbPolicy(
diff --git a/test/cpp/interop/client.cc b/test/cpp/interop/client.cc
index 874e7bc7b7a..cf3ada95b03 100644
--- a/test/cpp/interop/client.cc
+++ b/test/cpp/interop/client.cc
@@ -70,6 +70,7 @@ ABSL_FLAG(
     //"long_lived_channel: sends large_unary rpcs over a long-lived channel;\n"
     //"oauth2_auth_token: raw oauth2 access token auth;\n"
     //"orca_per_rpc: custom LB policy receives per-query metric reports;\n"
+    //"orca_oob: receives out-of-band metric reports from the backend;\n"
     //"per_rpc_creds: raw oauth2 access token on a single rpc;\n"
     //"ping_pong : full-duplex streaming;\n"
     //"response streaming;\n"
@@ -271,6 +272,8 @@ int main(int argc, char** argv) {
       std::bind(&grpc::testing::InteropClient::DoPickFirstUnary, &client);
   actions["orca_per_rpc"] =
       std::bind(&grpc::testing::InteropClient::DoOrcaPerRpc, &client);
+  actions["orca_oob"] =
+      std::bind(&grpc::testing::InteropClient::DoOrcaOob, &client);
   if (absl::GetFlag(FLAGS_use_tls)) {
     actions["compute_engine_creds"] =
         std::bind(&grpc::testing::InteropClient::DoComputeEngineCreds, &client,
diff --git a/test/cpp/interop/interop_client.cc b/test/cpp/interop/interop_client.cc
index 87721d3e253..a720e77e03a 100644
--- a/test/cpp/interop/interop_client.cc
+++ b/test/cpp/interop/interop_client.cc
@@ -25,8 +25,10 @@
 #include <type_traits>
 #include <utility>
 
+#include "absl/cleanup/cleanup.h"
 #include "absl/strings/match.h"
 #include "absl/strings/str_format.h"
+#include "absl/strings/str_join.h"
 
 #include <grpc/grpc.h>
 #include <grpc/support/alloc.h>
@@ -98,38 +100,61 @@ void InitializeCustomLbPolicyIfNeeded() {
   }
 }
 
+absl::optional<std::string> ValuesDiff(absl::string_view field, double expected,
+                                       double actual) {
+  if (expected != actual) {
+    return absl::StrFormat("%s: expected: %f, actual: %f", field, expected,
+                           actual);
+  }
+  return absl::nullopt;
+}
+
 template <typename Map>
-bool SameMaps(const std::string& path, const Map& expected, const Map& actual) {
-  if (expected.size() != actual.size()) {
-    gpr_log(GPR_ERROR, "Field %s does not match: expected %lu entries, got %lu",
-            path.c_str(), expected.size(), actual.size());
-    return false;
+absl::optional<std::string> MapsDiff(absl::string_view path,
+                                     const Map& expected, const Map& actual) {
+  auto result = ValuesDiff(absl::StrFormat("%s size", path), expected.size(),
+                           actual.size());
+  if (result.has_value()) {
+    return result;
   }
   for (const auto& key_value : expected) {
     auto it = actual.find(key_value.first);
     if (it == actual.end()) {
-      gpr_log(GPR_ERROR, "In field %s, key %s was not found", path.c_str(),
-              key_value.first.c_str());
-      return false;
+      return absl::StrFormat("In field %s, key %s was not found", path,
+                             key_value.first);
     }
-    if (key_value.second != it->second) {
-      gpr_log(
-          GPR_ERROR, "In field %s, value %s mismatch: expected %f, actual: %f",
-          path.c_str(), key_value.first.c_str(), key_value.second, it->second);
-      return false;
+    result = ValuesDiff(absl::StrFormat("%s/%s", path, key_value.first),
+                        key_value.second, it->second);
+    if (result.has_value()) {
+      return result;
     }
   }
-  return true;
+  return absl::nullopt;
 }
 
-void SameOrcaLoadReports(const xds::data::orca::v3::OrcaLoadReport& expected,
-                         const xds::data::orca::v3::OrcaLoadReport& actual) {
-  GPR_ASSERT(expected.cpu_utilization() == actual.cpu_utilization());
-  GPR_ASSERT(expected.mem_utilization() == actual.mem_utilization());
-  GPR_ASSERT(
-      SameMaps("request_cost", expected.request_cost(), actual.request_cost()));
-  GPR_ASSERT(
-      SameMaps("utilization", expected.utilization(), actual.utilization()));
+absl::optional<std::string> OrcaLoadReportsDiff(
+    const xds::data::orca::v3::OrcaLoadReport& expected,
+    const xds::data::orca::v3::OrcaLoadReport& actual) {
+  auto error = ValuesDiff("cpu_utilization", expected.cpu_utilization(),
+                          actual.cpu_utilization());
+  if (error.has_value()) {
+    return error;
+  }
+  error = ValuesDiff("mem_utilization", expected.mem_utilization(),
+                     actual.mem_utilization());
+  if (error.has_value()) {
+    return error;
+  }
+  error =
+      MapsDiff("request_cost", expected.request_cost(), actual.request_cost());
+  if (error.has_value()) {
+    return error;
+  }
+  error = MapsDiff("utilization", expected.utilization(), actual.utilization());
+  if (error.has_value()) {
+    return error;
+  }
+  return absl::nullopt;
 }
 }  // namespace
 
@@ -1006,12 +1031,81 @@ bool InteropClient::DoOrcaPerRpc() {
   auto report = load_report_tracker_.GetNextLoadReport();
   GPR_ASSERT(report.has_value());
   GPR_ASSERT(report->has_value());
-  SameOrcaLoadReports(report->value(), *orca_report);
+  auto comparison_result = OrcaLoadReportsDiff(report->value(), *orca_report);
+  if (comparison_result.has_value()) {
+    gpr_assertion_failed(__FILE__, __LINE__, comparison_result->c_str());
+  }
   GPR_ASSERT(!load_report_tracker_.GetNextLoadReport().has_value());
   gpr_log(GPR_DEBUG, "orca per rpc successfully finished");
   return true;
 }
 
+bool InteropClient::DoOrcaOob() {
+  gpr_log(GPR_DEBUG, "testing orca oob");
+  ClientContext context;
+  std::unique_ptr<ClientReaderWriter<StreamingOutputCallRequest,
+                                     StreamingOutputCallResponse>>
+      stream(serviceStub_.Get()->FullDuplexCall(&context));
+  auto stream_cleanup = absl::MakeCleanup([&]() {
+    GPR_ASSERT(stream->WritesDone());
+    GPR_ASSERT(stream->Finish().ok());
+  });
+  {
+    StreamingOutputCallRequest request;
+    request.add_response_parameters()->set_size(1);
+    xds::data::orca::v3::OrcaLoadReport* orca_report =
+        request.mutable_orca_oob_report();
+    orca_report->set_cpu_utilization(0.8210);
+    orca_report->set_mem_utilization(0.5847);
+    orca_report->mutable_utilization()->emplace("util", 0.30499);
+    StreamingOutputCallResponse response;
+    if (!stream->Write(request)) {
+      gpr_log(GPR_ERROR, "DoOrcaOob(): stream->Write() failed");
+      return TransientFailureOrAbort();
+    }
+    if (!stream->Read(&response)) {
+      gpr_log(GPR_ERROR, "DoOrcaOob(): stream->Read failed");
+      return TransientFailureOrAbort();
+    }
+    GPR_ASSERT(
+        load_report_tracker_
+            .WaitForOobLoadReport(
+                [orca_report](const auto& actual) {
+                  return !OrcaLoadReportsDiff(*orca_report, actual).has_value();
+                },
+                absl::Seconds(5), 10)
+            .has_value());
+  }
+  {
+    StreamingOutputCallRequest request;
+    request.add_response_parameters()->set_size(1);
+    xds::data::orca::v3::OrcaLoadReport* orca_report =
+        request.mutable_orca_oob_report();
+    orca_report->set_cpu_utilization(0.29309);
+    orca_report->set_mem_utilization(0.2);
+    orca_report->mutable_utilization()->emplace("util", 0.2039);
+    StreamingOutputCallResponse response;
+    if (!stream->Write(request)) {
+      gpr_log(GPR_ERROR, "DoOrcaOob(): stream->Write() failed");
+      return TransientFailureOrAbort();
+    }
+    if (!stream->Read(&response)) {
+      gpr_log(GPR_ERROR, "DoOrcaOob(): stream->Read failed");
+      return TransientFailureOrAbort();
+    }
+    GPR_ASSERT(
+        load_report_tracker_
+            .WaitForOobLoadReport(
+                [orca_report](const auto& report) {
+                  return !OrcaLoadReportsDiff(*orca_report, report).has_value();
+                },
+                absl::Seconds(5), 10)
+            .has_value());
+  }
+  gpr_log(GPR_DEBUG, "orca oob successfully finished");
+  return true;
+}
+
 bool InteropClient::DoCustomMetadata() {
   const std::string kEchoInitialMetadataKey("x-grpc-test-echo-initial");
   const std::string kInitialMetadataValue("test_initial_metadata_value");
diff --git a/test/cpp/interop/interop_client.h b/test/cpp/interop/interop_client.h
index 4fc7d79dd82..37915b62082 100644
--- a/test/cpp/interop/interop_client.h
+++ b/test/cpp/interop/interop_client.h
@@ -78,6 +78,7 @@ class InteropClient {
   // all requests are sent to one server despite multiple servers are resolved
   bool DoPickFirstUnary();
   bool DoOrcaPerRpc();
+  bool DoOrcaOob();
 
   // The following interop test are not yet part of the interop spec, and are
   // not implemented cross-language. They are considered experimental for now,
diff --git a/test/cpp/interop/interop_server.cc b/test/cpp/interop/interop_server.cc
index 7383c68d7c4..af4e51d8f9d 100644
--- a/test/cpp/interop/interop_server.cc
+++ b/test/cpp/interop/interop_server.cc
@@ -27,6 +27,7 @@
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>
 #include <grpcpp/ext/call_metric_recorder.h>
+#include <grpcpp/ext/orca_service.h>
 #include <grpcpp/ext/server_metric_recorder.h>
 #include <grpcpp/security/server_credentials.h>
 #include <grpcpp/server.h>
@@ -139,8 +140,9 @@ bool CheckExpectedCompression(const ServerContext& context,
   return true;
 }
 
-void RecordMetrics(ServerContext* context,
-                   const xds::data::orca::v3::OrcaLoadReport& request_metrics) {
+void RecordCallMetrics(
+    ServerContext* context,
+    const xds::data::orca::v3::OrcaLoadReport& request_metrics) {
   auto recorder = context->ExperimentalGetCallMetricRecorder();
   // Do not record when zero since it indicates no test per-call report.
   if (request_metrics.cpu_utilization() > 0) {
@@ -170,6 +172,10 @@ void RecordMetrics(ServerContext* context,
 
 class TestServiceImpl : public TestService::Service {
  public:
+  explicit TestServiceImpl(
+      grpc::experimental::ServerMetricRecorder* server_metric_recorder)
+      : server_metric_recorder_(server_metric_recorder) {}
+
   Status EmptyCall(ServerContext* context,
                    const grpc::testing::Empty* /*request*/,
                    grpc::testing::Empty* /*response*/) override {
@@ -220,7 +226,7 @@ class TestServiceImpl : public TestService::Service {
           request->response_status().message());
     }
     if (request->has_orca_per_rpc_report()) {
-      RecordMetrics(context, request->orca_per_rpc_report());
+      RecordCallMetrics(context, request->orca_per_rpc_report());
     }
     return Status::OK;
   }
@@ -313,6 +319,9 @@ class TestServiceImpl : public TestService::Service {
         }
         write_success = stream->Write(response);
       }
+      if (request.has_orca_oob_report()) {
+        RecordServerMetrics(request.orca_oob_report());
+      }
     }
     if (write_success) {
       return Status::OK;
@@ -349,6 +358,35 @@ class TestServiceImpl : public TestService::Service {
       return Status(grpc::StatusCode::INTERNAL, "Error writing response.");
     }
   }
+
+ private:
+  void RecordServerMetrics(
+      const xds::data::orca::v3::OrcaLoadReport& request_metrics) {
+    // Do not record when zero since it indicates no test per-call report.
+    if (request_metrics.cpu_utilization() > 0) {
+      server_metric_recorder_->SetCpuUtilization(
+          request_metrics.cpu_utilization());
+    }
+    if (request_metrics.mem_utilization() > 0) {
+      server_metric_recorder_->SetMemoryUtilization(
+          request_metrics.mem_utilization());
+    }
+    if (request_metrics.rps_fractional() > 0) {
+      server_metric_recorder_->SetQps(request_metrics.rps_fractional());
+    }
+    absl::MutexLock lock(&retained_utilization_names_mu_);
+    std::map<grpc::string_ref, double> named_utilizations;
+    for (const auto& p : request_metrics.utilization()) {
+      const auto& key = *retained_utilization_names_.insert(p.first).first;
+      named_utilizations.emplace(key, p.second);
+    }
+    server_metric_recorder_->SetAllNamedUtilization(named_utilizations);
+  }
+
+  grpc::experimental::ServerMetricRecorder* server_metric_recorder_;
+  std::set<std::string> retained_utilization_names_
+      ABSL_GUARDED_BY(retained_utilization_names_mu_);
+  absl::Mutex retained_utilization_names_mu_;
 };
 
 void grpc::testing::interop::RunServer(
@@ -378,13 +416,16 @@ void grpc::testing::interop::RunServer(
   GPR_ASSERT(port != 0);
   std::ostringstream server_address;
   server_address << "0.0.0.0:" << port;
-  TestServiceImpl service;
-
-  SimpleRequest request;
-  SimpleResponse response;
-
+  auto server_metric_recorder =
+      grpc::experimental::ServerMetricRecorder::Create();
+  TestServiceImpl service(server_metric_recorder.get());
+  grpc::experimental::OrcaService orca_service(
+      server_metric_recorder.get(),
+      experimental::OrcaService::Options().set_min_report_duration(
+          absl::Seconds(0.1)));
   ServerBuilder builder;
   builder.RegisterService(&service);
+  builder.RegisterService(&orca_service);
   builder.AddListeningPort(server_address.str(), creds);
   if (server_options != nullptr) {
     for (size_t i = 0; i < server_options->size(); i++) {
@@ -395,7 +436,7 @@ void grpc::testing::interop::RunServer(
     builder.SetMaxSendMessageSize(absl::GetFlag(FLAGS_max_send_message_size));
   }
   grpc::ServerBuilder::experimental_type(&builder).EnableCallMetricRecording(
-      nullptr);
+      server_metric_recorder.get());
   std::unique_ptr<Server> server(builder.BuildAndStart());
   gpr_log(GPR_INFO, "Server listening on %s", server_address.str().c_str());