On a lightly floured surface, roll dough into a 16x11-in. rectangle. Transfer to a greased 15x10x1-in. baking pan. Build up edges slightly. Cover and let rise 30 minutes.
Preheat oven to 425°. Brush oil over dough; sprinkle with garlic salt. Spread with a thin layer of salad dressing. Combine the cheeses; sprinkle over dressing. Layer with tomatoes, green pepper, onion, olives and mushrooms. Sprinkle with salt, basil, oregano, pepper and Parmesan cheese.
Bake 20-25 minutes or until crust is golden brown and cheese is melted. Cut into squares. Yield: 24 slices.