In a bowl, combine the flour, salt, garlic powder and pepper; stir in milk and eggs. Pour into a greased 13x9-in. baking pan. In a skillet, cook sausage over medium heat until no longer pink; drain. Sprinkle over the crust. Top with pepperoni, onion and green pepper., Bake, uncovered, at 425° for 15 minutes or until a toothpick inserted in the center comes out clean. Spread with pizza sauce and sprinkle with cheese. Bake 5 minutes longer or until cheese is melted. Let stand for 5 minutes before cutting.