Prepare a 12" round pizza pan with cooking spray; set aside. On a lightly floured surface, roll dough out to a 12" circle. Place in prepared pan, pressing to fit edges. Prick several time with a fork. Bake in a 425 degree oven for 15 minutes, or until light brown. Remove from oven and set aside. Prepare a large skillet, with cooking spray. In a mixing bowl, combine egg whites, onions, bell peppers, garlic powder, salt, and black pepper. Mix well. Add mixture to hot skillet. Cook until egg whites are done. Remove from skillet. Re-spray skillet and add hash browns. Cook until browned. Cover crust with cooked egg white mixture, hash browns, cooked sausage pieces, and cheeses. Bake for ten mintues more or until cheese has melted.