diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d5ad0f9d2..0c4a80bf3 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -524,20 +524,22 @@ jobs:
             cc_compiler: /usr/local/opt/llvm/bin/clang
             cxx_compiler: /usr/local/opt/llvm/bin/clang++
             cxx_std: 17
-            openimageio_ver: release
+            # openimageio_ver: release
             python_ver: "3.11"
             aclang: 14
             setenvs: export DO_BREW_UPDATE=1 CTEST_TEST_TIMEOUT=120
+                            EXTRA_BREW_PACKAGES="openimageio"
           - desc: MacOS-14-ARM llvm17
             runner: macos-14
             nametag: macos14-arm-p311
             cc_compiler: clang
             cxx_compiler: clang++
             cxx_std: 17
-            openimageio_ver: main
+            # openimageio_ver: main
             python_ver: "3.11"
             aclang: 15
             setenvs: export DO_BREW_UPDATE=1
+                            EXTRA_BREW_PACKAGES="openimageio"
           - desc: MacOS-15-ARM aclang16/C++20/py3.13
             runner: macos-15
             nametag: macos15-arm-py313
@@ -545,6 +547,7 @@ jobs:
             cxx_compiler: clang++
             cxx_std: 20
             python_ver: "3.13"
+            openimageio_ver: main
 
 
   windows:
diff --git a/src/build-scripts/gh-win-installdeps.bash b/src/build-scripts/gh-win-installdeps.bash
index 9b44a2f72..871f4dc20 100755
--- a/src/build-scripts/gh-win-installdeps.bash
+++ b/src/build-scripts/gh-win-installdeps.bash
@@ -117,16 +117,29 @@ cp $DEP_DIR/lib/*.lib $DEP_DIR/bin
 cp $DEP_DIR/bin/*.dll $DEP_DIR/lib
 
 
-#OPENIMAGEIO_BRANCH=lg-cmake312
-OPENIMAGEIO_INSTALLDIR=$DEP_DIR
-OPENIMAGEIO_CMAKE_FLAGS+=" -DOIIO_BUILD_TESTS=0 -DOIIO_BUILD_TOOLS=0"
-OPENIMAGEIO_CMAKE_FLAGS+=" -DUSE_OPENGL=0 -DUSE_GENERATED_EXPORT_HEADER=1"
-OPENIMAGEIO_CMAKE_FLAGS+=" -DENABLE_DPX=0 -DENABLE_CINEON=0 -DENABLE_DDS=0"
-OPENIMAGEIO_CMAKE_FLAGS+=" -DENABLE_IFF=0 -DENABLE_ICO=0 -DENABLE_PSD=0"
-OPENIMAGEIO_CMAKE_FLAGS+=" -DENABLE_PNM=0 -DENABLE_ZFILE=0 -DENABLE_SOFTIMAGE=0"
-OPENIMAGEIO_CMAKE_FLAGS+=" -DLINKSTATIC=1 -DBUILD_SHARED_LIBS=0"
-export OPENIMAGEIO_CMAKE_FLAGS
-source src/build-scripts/build_openimageio.bash
+if [[ "$OPENIMAGEIO_VERSION" != "" ]] ; then
+    # There are many parts of OIIO we don't need to build for OSL's tests
+    export ENABLE_iinfo=0 ENABLE_iv=0 ENABLE_igrep=0
+    export ENABLE_iconvert=0 ENABLE_testtex=0
+    # For speed of compiling OIIO, disable the file formats that we don't
+    # need for OSL's tests
+    export ENABLE_BMP=0 ENABLE_cineon=0 ENABLE_DDS=0 ENABLE_DPX=0 ENABLE_FITS=0
+    export ENABLE_ICO=0 ENABLE_iff=0 ENABLE_jpeg2000=0 ENABLE_PNM=0 ENABLE_PSD=0
+    export ENABLE_RLA=0 ENABLE_SGI=0 ENABLE_SOCKET=0 ENABLE_SOFTIMAGE=0
+    export ENABLE_TARGA=0 ENABLE_WEBP=0 ENABLE_jpegxl=0 ENABLE_libuhdr=0
+    # We don't need to run OIIO's tests
+    export OPENIMAGEIO_CMAKE_FLAGS+=" -DOIIO_BUILD_TESTING=OFF -DOIIO_BUILD_TESTS=0"
+    # Don't let warnings in OIIO break OSL's CI run
+    export OPENIMAGEIO_CMAKE_FLAGS+=" -DSTOP_ON_WARNING=OFF"
+    export OPENIMAGEIO_CMAKE_FLAGS+=" -DUSE_OPENGL=0"
+    export OPENIMAGEIO_CMAKE_FLAGS+=" -DUSE_OPENCV=0 -DUSE_FFMPEG=0 -DUSE_QT=0"
+    if [[ "${OPENIMAGEIO_UNITY:-1}" != "0" ]] ; then
+        # Speed up the OIIO build by doing a "unity" build. (Note: this is
+        # only a savings in CI where there are only 1-2 cores available.)
+        export OPENIMAGEIO_CMAKE_FLAGS+=" -DCMAKE_UNITY_BUILD=ON -DCMAKE_UNITY_BUILD_MODE=BATCH"
+    fi
+    source src/build-scripts/build_openimageio.bash
+fi
 
 
 cp $DEP_DIR/lib/*.lib $DEP_DIR/bin
diff --git a/src/build-scripts/install_homebrew_deps.bash b/src/build-scripts/install_homebrew_deps.bash
index 46b8f94b8..434219eae 100755
--- a/src/build-scripts/install_homebrew_deps.bash
+++ b/src/build-scripts/install_homebrew_deps.bash
@@ -48,6 +48,9 @@ brew install --display-times -q llvm${LLVMBREWVER}
 if [[ "${USE_QT}" != "0" ]] ; then
     brew install --display-times -q qt${QT_VERSION}
 fi
+if [[ "${EXTRA_BREW_PACKAGES}" != "" ]] ; then
+    brew install --display-times -q ${EXTRA_BREW_PACKAGES}
+fi
 
 echo ""
 echo "After brew installs:"