Pre-heat the oven to 350 degrees. In a large skillet add oil and heat to medium-high heat. Add ground beef, onion, and garlic. Add Italian seasoning. Cook until the beef is browned. Drain.
Stir in pasta sauce and 3 cups of cheese into the meat mixture. Place mixture into 2 greased 9×13” baking dishes.
Sprinkle with the remaining mozzarella cheese and top with pepperoni. *The dish can be covered and frozen at this point if you are freezing.
If you are cooking it now- Bake in the oven at 350 degrees for 25-30 minutes.