In a greased 13-in. x 9-in. baking dish, place onion and chicken breast; sprinkle with salt if desired and pepper. Layer mushrooms and zucchini over chicken. Combine the garlic, tomatoes, basil and oregano; pour over vegetables.
Cover tightly. Bake at 450° for 30 minutes or until juices run clear. Sprinkle with Parmesan cheese if desired.