Preheat oven to 350°F. Spray a 9" x 9" baking dish with non-stick spray.

Place ground beef, Italian sausage, green pepper and onion in a large skillet. TIP: If using Italian sausage links, remove the casing. Cook on medium-high heat until meat is browned/fully cooked. Drain grease from skillet. Season meat with Italian seasoning, salt and pepper. Stir well.

Transfer meat mixture to large bowl; add marinara sauce and 1½ cups mozzarella. Note: Reserve ½ cup mozzarella to use later! Stir mixture well, until combined.

Bring large pan of water to a full boil. Add pasta; cook on medium-high heat per pkg. directions (approx. 10 minutes). Pasta may be slightly undercooked but will finish cooking in the oven. Drain pasta; add to meat sauce in bowl. Stir well, to coat pasta with meat sauce.

Pour casserole filling into greased baking dish, spreading mixture evenly. Top with remaining mozzarella cheese, sprinkling evenly. Cover dish with aluminum foil.

Bake at 350°F. for 35-40 minutes, removing foil during the last 10 minutes of baking. It's done when the sauce is bubbly around the edges and cheese topping is golden brown and fully melted. Transfer baking dish to a wire rack. Let casserole rest 2-3 minutes before serving. If desired, sprinkle each portion with grated Parmesan cheese. Serve and enjoy!