diff --git a/templates/tools/dockerfile/test/python_stretch_default_x64/Dockerfile.template b/templates/tools/dockerfile/test/python_stretch_default_x64/Dockerfile.template
index ccb88e75302..bb4a9f29c01 100644
--- a/templates/tools/dockerfile/test/python_stretch_default_x64/Dockerfile.template
+++ b/templates/tools/dockerfile/test/python_stretch_default_x64/Dockerfile.template
@@ -16,7 +16,11 @@
 
   <%include file="../../python_stretch.include"/>
   <%include file="../../compile_python_36.include"/>
-  
+  <%include file="../../compile_python_38.include"/>
+
+  RUN apt-get update && apt-get install -y python3.5 python3.5-dev
+  RUN curl https://bootstrap.pypa.io/get-pip.py | python3.5
+
   RUN apt-get update && apt-get -t buster install -y python3.7 python3-all-dev
   RUN curl https://bootstrap.pypa.io/get-pip.py | python3.7
 
diff --git a/tools/dockerfile/test/python_stretch_default_x64/Dockerfile b/tools/dockerfile/test/python_stretch_default_x64/Dockerfile
index 9a1d6c09deb..713fd6fe230 100644
--- a/tools/dockerfile/test/python_stretch_default_x64/Dockerfile
+++ b/tools/dockerfile/test/python_stretch_default_x64/Dockerfile
@@ -84,6 +84,29 @@ RUN cd /tmp && \
 RUN python3.6 -m ensurepip && \
     python3.6 -m pip install coverage
 
+#=================
+# Compile CPython 3.8.0b4 from source
+
+RUN apt-get update && apt-get install -y zlib1g-dev libssl-dev
+RUN apt-get update && apt-get install -y jq build-essential libffi-dev
+
+RUN cd /tmp && \
+    wget -q https://www.python.org/ftp/python/3.8.0/Python-3.8.0b4.tgz && \
+    tar xzvf Python-3.8.0b4.tgz && \
+    cd Python-3.8.0b4 && \
+    ./configure && \
+    make install
+
+RUN cd /tmp && \
+    echo "b8f4f897df967014ddb42033b90c3058 Python-3.8.0b4.tgz" > checksum.md5 && \
+    md5sum -c checksum.md5
+
+RUN python3.8 -m ensurepip && \
+    python3.8 -m pip install coverage
+
+
+RUN apt-get update && apt-get install -y python3.5 python3.5-dev
+RUN curl https://bootstrap.pypa.io/get-pip.py | python3.5
 
 RUN apt-get update && apt-get -t buster install -y python3.7 python3-all-dev
 RUN curl https://bootstrap.pypa.io/get-pip.py | python3.7
diff --git a/tools/run_tests/helper_scripts/build_python.sh b/tools/run_tests/helper_scripts/build_python.sh
index 670b5fc69d8..e79a8896092 100755
--- a/tools/run_tests/helper_scripts/build_python.sh
+++ b/tools/run_tests/helper_scripts/build_python.sh
@@ -165,24 +165,33 @@ pip_install_dir() {
   cd "$PWD"
 }
 
+# On library/version/platforms combo that do not have a binary
+# published, we may end up building a dependency from source. In that
+# case, several of our build environment variables may disrupt the
+# third-party build process. This function pipes through only the
+# minimal environment necessary.
+pip_install() {
+  /usr/bin/env -i PATH="$PATH" "$VENV_PYTHON" -m pip install "$@"
+}
+
 case "$VENV" in
   *py36_gevent*)
   # TODO(https://github.com/grpc/grpc/issues/15411) unpin this
-  $VENV_PYTHON -m pip install gevent==1.3.b1
+  pip_install gevent==1.3.b1
   ;;
   *gevent*)
-  $VENV_PYTHON -m pip install -U gevent
+  pip_install -U gevent
   ;;
 esac
 
-$VENV_PYTHON -m pip install --upgrade pip==19.3.1
-$VENV_PYTHON -m pip install --upgrade setuptools
-$VENV_PYTHON -m pip install --upgrade cython
-$VENV_PYTHON -m pip install --upgrade six enum34 protobuf
+pip_install --upgrade pip==19.3.1
+pip_install --upgrade setuptools
+pip_install --upgrade cython
+pip_install --upgrade six enum34 protobuf
 
 if [ "$("$VENV_PYTHON" -c "import sys; print(sys.version_info[0])")" == "2" ]
 then
-  $VENV_PYTHON -m pip install futures
+  pip_install futures
 fi
 
 pip_install_dir "$ROOT"
@@ -214,9 +223,9 @@ pip_install_dir "$ROOT/src/python/grpcio_status"
 pip_install_dir "$ROOT/src/python/grpcio_testing"
 
 # Build/install tests
-$VENV_PYTHON -m pip install coverage==4.4 oauth2client==4.1.0 \
-                            google-auth==1.0.0 requests==2.14.2 \
-                            googleapis-common-protos==1.5.5
+pip_install coverage==4.4 oauth2client==4.1.0 \
+            google-auth==1.0.0 requests==2.14.2 \
+            googleapis-common-protos==1.5.5
 $VENV_PYTHON "$ROOT/src/python/grpcio_tests/setup.py" preprocess
 $VENV_PYTHON "$ROOT/src/python/grpcio_tests/setup.py" build_package_protos
 pip_install_dir "$ROOT/src/python/grpcio_tests"
diff --git a/tools/run_tests/run_tests.py b/tools/run_tests/run_tests.py
index a3d255110f0..b1c56762bd1 100755
--- a/tools/run_tests/run_tests.py
+++ b/tools/run_tests/run_tests.py
@@ -866,9 +866,19 @@ class PythonLanguage(object):
             else:
                 if args.iomgr_platform == 'asyncio':
                     return (python36_config,)
+                elif os.uname()[0] == 'Darwin':
+                    # NOTE(rbellevi): Testing takes significantly longer on
+                    # MacOS, so we restrict the number of interpreter versions
+                    # tested.
+                    return (
+                        python27_config,
+                        python36_config,
+                        python37_config,
+                    )
                 else:
                     return (
                         python27_config,
+                        python35_config,
                         python36_config,
                         python37_config,
                     )