Preheat Oven: Preheat oven to 375°F (190°C) and grease a 9x13-inch baking dish.
Cook Pasta: Boil penne pasta according to package instructions until al dente. Drain and set aside.
Brown Meat: In a large skillet, cook Italian sausage and ground beef over medium heat until browned. Drain excess fat.
Sauté Veggies: Add onions, bell peppers, and garlic to the skillet. Cook for 3-4 minutes until softened.
Combine Ingredients: Stir in marinara sauce, Italian seasoning, salt, and pepper. Mix well.
Layer Casserole:
Spread cooked pasta in the baking dish.
Pour meat and sauce mixture over the pasta.
Top with pepperoni, black olives, and cheeses.
Bake: Cover with foil and bake for 20 minutes. Remove foil and bake for 10 more minutes until cheese is bubbly and golden.
Serve: Let cool for 5 minutes, then slice and serve!