1. Preheat oven to 400°F. In a large skillet over medium heat, break up sausage and cook until it is brown.
  2. Remove sausage from pan and set aside. Add bell peppers, onions, and garlic and cook, stirring often, until slightly soft, about 5 minutes.
  3. Add mushrooms and cook about 5 more minutes.
  4. Remove pan from heat and add sausage, pepperoni, pizza sauce, and mozzarella and stir until completely combined.
  5. Add filling to a pie dish and lay the pizza dough on top. Sprinkle some cheese and a few pieces of pepperoni on top.
  6. Cover with foil and bake for 30 minutes. Uncover and bake for an additional 10 minutes until crust is golden brown.
  7. Top with fresh parsley and serve.