Heat oven to 425 degrees. Split each pita bread in half around edge to make 4 rounds. Place rounds, cut-sides up on ungreased cookie sheet. Place mushrooms on bread rounds. Top with onion and bell pepper. Sprinkle with basil and cheeses. Bake 8 to 10 minutes or until cheese is melted. Cut each round into 8 pieces. Makes 32 appetizers. Preparation time: 10 minutes Baking time: 8 to 10 minutes