Heat oven to 400°F. Lightly spray 9x5-inch (1 1/2-quart) glass loaf dish with cooking spray. Sprinkle zucchini, tomato, onion and cheese in dish.
In medium bowl, stir remaining ingredients until blended. Pour over vegetables and cheese.
Bake 30 to 35 minutes or until knife inserted in center comes out clean. Cool 5 minutes before serving.