Preheat the oven to 400 degrees F.
In a large saute pan, over medium heat, add 2 tablespoons of the olive oil. When the oil is hot, add the onions. Season with salt and pepper and saute for 2 minutes. Add the peppers, season with salt and pepper, and continue to saute for 3 minutes. Remove from the heat. Transfer to a bowl and set aside.
Lay 1/4-pound of the sliced provolone on the bottom of each pizza. Spoon 1/2 the onion and pepper mixture over each pizza. Sprinkle 1/2 of the sausage over the onion mixture on each pizza. Scatter 1 cup sliced mushrooms over sausage. Spread 1 cup of the tomato sauce over the top of each pizza. Layer 1/4-pound mozzarella slices over top of each pizza. Drizzle with remaining olive oil. Bake the pizzas for 25 to 30 minutes or until golden brown.
Remove the pizza from the oven and cut into individual servings.
Yield: dough for 2 (12-inch) pizzas