Preheat oven to 350. Prepare a toaster oven tray with cooking spray. Press biscuits onto bottom and sides of prepared pan to form a crust. Bake for seven minutes. Remove from oven. Spoon tomato sauce onto partially baked crust. In a skillet, over medium heat, cook chicken until no longer pink. Add Italian seasoning, pizza seasoning, and garlic powder. Cook until chicken is no longer pink. Spread meat mixture onto crust. Sprinkle with mushrooms, onions, bell peppers, and cheese. Bake for 20 minutes or until crust is brown and cheese has melted.