1Heat oven to 425°F. Grease 10-inch glass pie plate with shortening or cooking spray. Sprinkle mushrooms, 2/3 cup of the onion and 1/3 cup Parmesan cheese in pie plate.
2In medium bowl, beat milk, eggs and Bisquick mix with wire whisk or electric mixer about 1 minute or until smooth. Pour over vegetable mixture in pie plate.
3Bake 20 minutes. Spread pizza sauce over top. Top with 1/4 cup Parmesan cheese, remaining 1/3 cup onion, the bell pepper and mozzarella cheese. Bake 15 to 20 minutes longer or until cheese is light brown. Let stand 5 minutes before cutting.