diff --git a/packages/react-native-codegen/BUCK b/packages/react-native-codegen/BUCK
index ca38d2bb4dc..008e47e870e 100644
--- a/packages/react-native-codegen/BUCK
+++ b/packages/react-native-codegen/BUCK
@@ -1,10 +1,7 @@
-load("@fbsource//tools/build_defs:fb_native_wrapper.bzl", "fb_native")
-load("@fbsource//tools/build_defs:fb_xplat_cxx_binary.bzl", "fb_xplat_cxx_binary")
-load("@fbsource//tools/build_defs:platform_defs.bzl", "ANDROID", "APPLE", "IOS")
-load("@fbsource//tools/build_defs/oss:rn_defs.bzl", "rn_android_library", "rn_xplat_cxx_library")
-load("@fbsource//tools/build_defs/third_party:yarn_defs.bzl", "yarn_workspace")
-load("@fbsource//xplat/js/react-native-github/packages/react-native-codegen:DEFS.bzl", "rn_codegen_components", "rn_codegen_modules")
-load("//tools/build_defs/oss:rn_defs.bzl", "react_native_target")
+load("//tools/build_defs:fb_native_wrapper.bzl", "fb_native")
+load("//tools/build_defs/oss:rn_defs.bzl", "ANDROID", "APPLE", "IOS", "react_native_target", "rn_android_library", "rn_xplat_cxx_library")
+load("//tools/build_defs/third_party:yarn_defs.bzl", "yarn_workspace")
+load(":DEFS.bzl", "rn_codegen_components", "rn_codegen_modules")
 
 fb_native.sh_binary(
     name = "codegen_rn_modules_tests",
@@ -74,26 +71,6 @@ rn_codegen_modules(
     schema_target = ":codegen_tests_schema",
 )
 
-fb_xplat_cxx_binary(
-    name = "rn_codegen_binary",
-    srcs = ["buck_tests/emptyFile.cpp"],
-    compiler_flags = [
-        "-fexceptions",
-        "-frtti",
-        "-std=c++14",
-        "-Wall",
-    ],
-    platforms = (ANDROID, APPLE),
-    preprocessor_flags = [
-        "-DLOG_TAG=\"ReactNative\"",
-        "-DWITH_FBSYSTRACE=1",
-    ],
-    visibility = ["PUBLIC"],
-    deps = [
-        ":generated_components-codegen_tests",
-    ],
-)
-
 rn_android_library(
     name = "rn_codegen_library_java",
     srcs = glob(
diff --git a/packages/react-native-codegen/DEFS.bzl b/packages/react-native-codegen/DEFS.bzl
index 17ce53e7e89..c1be64cfdd4 100644
--- a/packages/react-native-codegen/DEFS.bzl
+++ b/packages/react-native-codegen/DEFS.bzl
@@ -1,16 +1,17 @@
-load("@fbsource//tools/build_defs:buckconfig.bzl", "read_bool")
-load("@fbsource//tools/build_defs:fb_native_wrapper.bzl", "fb_native")
-load("@fbsource//tools/build_defs:platform_defs.bzl", "IOS", "MACOSX")
-load("@fbsource//tools/build_defs/apple:flag_defs.bzl", "get_preprocessor_flags_for_build_mode")
+load("//tools/build_defs:buckconfig.bzl", "read_bool")
+load("//tools/build_defs:fb_native_wrapper.bzl", "fb_native")
 load(
     "//tools/build_defs/oss:rn_defs.bzl",
     "ANDROID",
     "APPLE",
     "CXX",
+    "IOS",
+    "MACOSX",
     "YOGA_CXX_TARGET",
     "fb_xplat_cxx_test",
     "get_apple_compiler_flags",
     "get_apple_inspector_flags",
+    "get_preprocessor_flags_for_build_mode",
     "react_native_dep",
     "react_native_target",
     "react_native_xplat_target",
diff --git a/tools/build_defs/buckconfig.bzl b/tools/build_defs/buckconfig.bzl
new file mode 100644
index 00000000000..939104966ed
--- /dev/null
+++ b/tools/build_defs/buckconfig.bzl
@@ -0,0 +1,38 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+def read(section, field, default = None):
+    """Read a `string` from `.buckconfig`."""
+
+    return native.read_config(section, field, default)
+
+def read_bool(section, field, default = None, required = True):
+    """Read a `boolean` from `.buckconfig`."""
+
+    # Treat the empty string as "unset".  This allows the user to "override" a
+    # previous setting by "clearing" it out.
+    val = read(section, field)
+    if val != None and val != "":
+        # Fast-path string check
+        if val == "True" or val == "true":
+            return True
+        elif val == "False" or val == "false":
+            return False
+
+        # Else fall back to lower casing
+        if val.lower() == "true":
+            return True
+        elif val.lower() == "false":
+            return False
+        else:
+            fail(
+                "`{}:{}`: cannot coerce {!r} to bool".format(section, field, val),
+            )
+    elif default != None:
+        return default
+    elif not required:
+        return None
+    else:
+        fail("`{}:{}`: no value set".format(section, field))
diff --git a/tools/build_defs/oss/rn_defs.bzl b/tools/build_defs/oss/rn_defs.bzl
index 7112b3a400e..336d264a864 100644
--- a/tools/build_defs/oss/rn_defs.bzl
+++ b/tools/build_defs/oss/rn_defs.bzl
@@ -27,9 +27,17 @@ GLOG_DEP = "//ReactAndroid/build/third-party-ndk/glog:glog"
 
 INSPECTOR_FLAGS = []
 
+# Platform Definitions
+CXX = "Default"
+
 ANDROID = "Android"
 
-APPLE = ""
+APPLE = "Apple"
+
+# Apple SDK Definitions
+IOS = "ios"
+
+MACOSX = "macosx"
 
 YOGA_TARGET = "//ReactAndroid/src/main/java/com/facebook:yoga"
 
diff --git a/tools/build_defs/third_party/yarn_defs.bzl b/tools/build_defs/third_party/yarn_defs.bzl
new file mode 100644
index 00000000000..cd31925f20f
--- /dev/null
+++ b/tools/build_defs/third_party/yarn_defs.bzl
@@ -0,0 +1,8 @@
+# Copyright (c) Facebook, Inc. and its affiliates.
+#
+# This source code is licensed under the MIT license found in the
+# LICENSE file in the root directory of this source tree.
+
+def yarn_workspace(name, srcs = [], transform_ignore = None, visibility = None):
+    # Noop for OSS vs FB build compatibility for now
+    unused = True