In casserole dish sprayed with Pam, layer slices of zucchini and yellow squash, tomatoes, mushrooms, and onion. Top with ½ cup Parmesan cheese, ½ cup bread crumbs, and dab 2 tbsp. butter over the top. Season with salt, pepper, and garlic powder. Bake uncovered at 350º F for 40-45 minutes.