In a large skillet, saute the mushrooms, peppers, olives, onions and garlic in 1 tablespoon oil until tender; remove and set aside. In the same skillet, cook beef and sausage over medium heat until no longer pink; drain.
Grease a 14-in. pizza pan and sprinkle with cornmeal. On a floured surface, roll dough into a 15-in. circle. Transfer to prepared pan.
Build up edges slightly; prick dough thoroughly with a fork. Brush with remaining oil; sprinkle with garlic powder. Bake at 400° for 8-10 minutes or until edges are lightly browned.
In a small bowl, combine the tomato sauce, parsley, Italian seasoning and pepper; spread over crust.
Top with the vegetables, meat mixture and pepperoni. Sprinkle with cheeses. Bake for 17-20 minutes or until crust is golden and cheese is melted.