Heat oven to 375°F. Grease 2 large or 3 small cookie sheets.
In 10-inch skillet, heat oil over medium-high heat. Cook bell pepper, mushrooms and onion in oil about 5 minutes, stirring occasionally, until limp; set aside. Place biscuits on cookie sheets. Press each to 6-inch round. Spread about 2 tablespoons pizza sauce on each; top each with cheese and veggies.
Bake 10 to 15 minutes or until bottoms are deep golden brown and cheese is bubbly.