I found this on an Illinois' newspaper website and the story was that this recipe eminated from Johnny Marzetti's diner, wherever that was, but now defunct. This is a great tasting dish, easy to fix and feeds the masses. Can easily be cut in half for smaller crowds.
Grease large baking dish and set aside. Pre-heat oven to 350F.
Prepare pasta according to instructions, drain and transfer to the baking dish.
Heat oil in large skillet over medium heat. Add celery, onion, bell pepper, salt and pepper to taste. Stir occasionally until softened, 5-7 minutes. Stir in garlic, oregano, pepper flakes and cook until fragrant, about 30 seconds.
Add beef and sausage, increase heat to medium-high and cook, breaking up clumps with a spoon until no longer pink, about 5 minutes. Stir in tomato sauce and diced tomatoes, bring to simmer and cook until flavors are blended about 3 minutes. Stir in parsley and season with more salt and pepper, if needed. Set aside, off heat.
Sprinkle 1 cup of cheese evenly over pasta, then pour meat mixture over top. Sprinkle remaining 1 cup of cheese on top of meat mixture.
Place the baking dish on a foil-lined baking sheet, cover with foil and bake for 45 minutes, until sauce is bubbling. Remove foil and bake 10 minutes more, until top is spotty brown. Cool 10 minutes before serving.