Preheat your oven to 350 degrees F. Grease a 2-quart baking dish or spray with cooking spray.
While pasta is cooking, cook ground beef, onion and green pepper in a dutch oven or large saucepan until meat is browned and no longer pink, crumbling beef while it cooks. Drain off fat.
Add cooked pasta, pizza sauce, 2 cups of the mozzarella cheese, pepperoni, mushrooms, olives, salt, pepper and Italian seasoning to beef mixture and stir well to combine.
Transfer to prepared baking dish. Sprinkle evenly with remaining 1 cup of mozzarella cheese.
Cover tightly with aluminum foil and bake for 30 minutes. Remove from oven, remove foil and bake for an additional 10 minutes, or until cheese is melted.
Sprinkle with fresh chopped parsley, if desired.