Place vegetables on a double thickness of heavy-duty foil (about 18 in. x 12 in.). Dot with butter; season with salt, pepper and garlic powder. Fold foil around vegetables and seal tightly.
Fold foil around vegetables and seal tightly. Grill, covered, over medium heat for 15-20 minutes or until vegetables are tender, turning once. Open foil carefully to allow steam to escape. Sprinkle with cheeses. Yield: 4 servings.