diff --git a/tools/internal_ci/helper_scripts/prepare_build_macos_rc b/tools/internal_ci/helper_scripts/prepare_build_macos_rc
index a13c29ea7f5..c497e33567f 100644
--- a/tools/internal_ci/helper_scripts/prepare_build_macos_rc
+++ b/tools/internal_ci/helper_scripts/prepare_build_macos_rc
@@ -27,62 +27,74 @@ if [ -n "$KOKORO_GITHUB_PULL_REQUEST_NUMBER" ]; then
   export RUN_TESTS_FLAGS="--filter_pr_tests --base_branch origin/$KOKORO_GITHUB_PULL_REQUEST_TARGET_BRANCH $RUN_TESTS_FLAGS"
 fi
 
-set +ex  # rvm script is very verbose and exits with errorcode
-# Advice from https://github.com/Homebrew/homebrew-cask/issues/8629#issuecomment-68641176
-brew update && brew upgrade brew-cask && brew cleanup && brew cask cleanup
-rvm --debug requirements ruby-2.5.0
-source $HOME/.rvm/scripts/rvm
-set -e  # rvm commands are very verbose
-time rvm install 2.5.0
-rvm use 2.5.0 --default
-time gem install bundler -v 1.17.3 --no-ri --no-doc
-time gem install cocoapods --version 1.3.1 --no-ri --no-doc
-time gem install rake-compiler --no-ri --no-doc
-rvm osx-ssl-certs status all
-rvm osx-ssl-certs update all
-set -ex
-
-# cocoapods
-export LANG=en_US.UTF-8
-# pre-fetch cocoapods master repo's most recent commit only
-mkdir -p ~/.cocoapods/repos
-time git clone --depth 1 https://github.com/CocoaPods/Specs.git ~/.cocoapods/repos/master
+if [ "${PREPARE_BUILD_INSTALL_DEPS_RUBY}" == "true" ]
+then
+  set +ex  # rvm script is very verbose and exits with errorcode
+  # Advice from https://github.com/Homebrew/homebrew-cask/issues/8629#issuecomment-68641176
+  brew update && brew upgrade brew-cask && brew cleanup && brew cask cleanup
+  rvm --debug requirements ruby-2.5.0
+  source $HOME/.rvm/scripts/rvm
+  set -e  # rvm commands are very verbose
+  time rvm install 2.5.0
+  rvm use 2.5.0 --default
+  time gem install bundler -v 1.17.3 --no-ri --no-doc
+  time gem install cocoapods --version 1.3.1 --no-ri --no-doc
+  time gem install rake-compiler --no-ri --no-doc
+  rvm osx-ssl-certs status all
+  rvm osx-ssl-certs update all
+  set -ex
+fi
 
-# python
-time pip install --user virtualenv
-time pip install --user --upgrade Mako six tox setuptools twisted pyyaml pyjwt cryptography requests
-export PYTHONPATH=/Library/Python/3.4/site-packages
+if [ "${PREPARE_BUILD_INSTALL_DEPS_OBJC}" == "true" ]
+then
+  # cocoapods
+  export LANG=en_US.UTF-8
+  # pre-fetch cocoapods master repo's most recent commit only
+  mkdir -p ~/.cocoapods/repos
+  time git clone --depth 1 https://github.com/CocoaPods/Specs.git ~/.cocoapods/repos/master
 
-# Install Python 3.7 and Python 3.8
-time curl -O https://www.python.org/ftp/python/3.7.0/python-3.7.0-macosx10.9.pkg
-time curl -O https://www.python.org/ftp/python/3.8.0/python-3.8.0-macosx10.9.pkg
-echo "ae0717a02efea3b0eb34aadc680dc498 python-3.7.0-macosx10.9.pkg" > /tmp/python_installer_checksum.md5
-echo "f5f9ae9f416170c6355cab7256bb75b5 python-3.8.0-macosx10.9.pkg" >> /tmp/python_installer_checksum.md5
-md5sum -c /tmp/python_installer_checksum.md5
-time sudo installer -pkg ./python-3.7.0-macosx10.9.pkg -target /
-time sudo installer -pkg ./python-3.8.0-macosx10.9.pkg -target /
+  # set xcode version for Obj-C tests
+  sudo xcode-select -switch /Applications/Xcode_9.2.app/Contents/Developer/
 
-# set xcode version for Obj-C tests
-sudo xcode-select -switch /Applications/Xcode_9.2.app/Contents/Developer/
+  # Store intermediate build files of ObjC tests into /tmpfs
+  # TODO(jtattermusch): why are we doing this?
+  mkdir /tmpfs/Build-ios-binary-size
+  ln -s /tmpfs/Build-ios-binary-size src/objective-c/examples/Sample/Build
+  mkdir -p /tmpfs/DerivedData
+  rm -rf ~/Library/Developer/Xcode/DerivedData
+  mkdir -p ~/Library/Developer/Xcode
+  ln -s /tmpfs/DerivedData ~/Library/Developer/Xcode/DerivedData
+fi
 
-# Disable some unwanted dotnet options
-export NUGET_XMLDOC_MODE=skip
-export DOTNET_SKIP_FIRST_TIME_EXPERIENCE=true
-export DOTNET_CLI_TELEMETRY_OPTOUT=true
+if [ "${PREPARE_BUILD_INSTALL_DEPS_PYTHON}" == "true" ]
+then
+  # python
+  time pip install --user virtualenv
+  time pip install --user --upgrade Mako six tox setuptools twisted pyyaml pyjwt cryptography requests
+  export PYTHONPATH=/Library/Python/3.4/site-packages
 
-# TODO(jtattermusch): better debugging of clock skew, remove once not needed
-date
-
-time git submodule update --init
+  # Install Python 3.7 and Python 3.8
+  time curl -O https://www.python.org/ftp/python/3.7.0/python-3.7.0-macosx10.9.pkg
+  time curl -O https://www.python.org/ftp/python/3.8.0/python-3.8.0-macosx10.9.pkg
+  echo "ae0717a02efea3b0eb34aadc680dc498 python-3.7.0-macosx10.9.pkg" > /tmp/python_installer_checksum.md5
+  echo "f5f9ae9f416170c6355cab7256bb75b5 python-3.8.0-macosx10.9.pkg" >> /tmp/python_installer_checksum.md5
+  md5sum -c /tmp/python_installer_checksum.md5
+  time sudo installer -pkg ./python-3.7.0-macosx10.9.pkg -target /
+  time sudo installer -pkg ./python-3.8.0-macosx10.9.pkg -target /
+fi
 
-# Store intermediate build files of ObjC tests into /tmpfs
-mkdir /tmpfs/Build-ios-binary-size
-ln -s /tmpfs/Build-ios-binary-size src/objective-c/examples/Sample/Build
-mkdir -p /tmpfs/DerivedData
-rm -rf ~/Library/Developer/Xcode/DerivedData
-mkdir -p ~/Library/Developer/Xcode
-ln -s /tmpfs/DerivedData ~/Library/Developer/Xcode/DerivedData
+if [ "${PREPARE_BUILD_INSTALL_DEPS_CSHARP}" == "true" ]
+then
+  # Disable some unwanted dotnet options
+  export NUGET_XMLDOC_MODE=skip
+  export DOTNET_SKIP_FIRST_TIME_EXPERIENCE=true
+  export DOTNET_CLI_TELEMETRY_OPTOUT=true
+fi
 
 # PHP tests currently require using an older version of PHPUnit
 ln -sf /usr/local/bin/phpunit-5.7 /usr/local/bin/phpunit
 
+# TODO(jtattermusch): better debugging of clock skew, remove once not needed
+date
+
+time git submodule update --init
diff --git a/tools/internal_ci/macos/grpc_basictests_csharp.cfg b/tools/internal_ci/macos/grpc_basictests_csharp.cfg
index d3e04e71f71..6c48a5bcf1f 100644
--- a/tools/internal_ci/macos/grpc_basictests_csharp.cfg
+++ b/tools/internal_ci/macos/grpc_basictests_csharp.cfg
@@ -15,7 +15,7 @@
 # Config file for the internal CI (in protobuf text format)
 
 # Location of the continuous shell script in repository.
-build_file: "grpc/tools/internal_ci/macos/grpc_run_tests_matrix.sh"
+build_file: "grpc/tools/internal_ci/macos/grpc_basictests_csharp.sh"
 gfile_resources: "/bigstore/grpc-testing-secrets/gcp_credentials/GrpcTesting-d0eeee2db331.json"
 timeout_mins: 60
 action {
diff --git a/tools/internal_ci/macos/grpc_basictests_csharp.sh b/tools/internal_ci/macos/grpc_basictests_csharp.sh
new file mode 100755
index 00000000000..c66e5c7738f
--- /dev/null
+++ b/tools/internal_ci/macos/grpc_basictests_csharp.sh
@@ -0,0 +1,19 @@
+#!/bin/bash
+# Copyright 2019 The gRPC Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -ex
+
+export PREPARE_BUILD_INSTALL_DEPS_CSHARP=true
+$(dirname $0)/grpc_run_tests_matrix.sh
diff --git a/tools/internal_ci/macos/pull_request/grpc_basictests_csharp.cfg b/tools/internal_ci/macos/pull_request/grpc_basictests_csharp.cfg
index c9c1403693c..5ee22e375d0 100644
--- a/tools/internal_ci/macos/pull_request/grpc_basictests_csharp.cfg
+++ b/tools/internal_ci/macos/pull_request/grpc_basictests_csharp.cfg
@@ -15,7 +15,7 @@
 # Config file for the internal CI (in protobuf text format)
 
 # Location of the continuous shell script in repository.
-build_file: "grpc/tools/internal_ci/macos/grpc_run_tests_matrix.sh"
+build_file: "grpc/tools/internal_ci/macos/grpc_basictests_csharp.sh"
 gfile_resources: "/bigstore/grpc-testing-secrets/gcp_credentials/GrpcTesting-d0eeee2db331.json"
 timeout_mins: 60
 action {