Over medium heat In a large skillet, cook the ground beef, ground sausage and onion until it is no longer pink and all large pieces are broken up. Add in the diced garlic and cook about one minute more.
Drain the meat. Add in the diced tomatoes, spaghetti sauce, canned mushrooms and the Italian seasoning. Bring this to a light simmer uncovered so it thickens up a bit for about 15- 20 minutes.
While the sauce is simmering preheat your oven to 350°. Cook the pasta according to the package directions to al dente. Drain the pasta.
Add the pasta to the beef mixture and gently mix.
Pour the mixture into a 13x9 baking dish and spread out evenly. Sprinkle the mozzarella and provolone cheese on top, then top it off last with the Parmesan cheese.
Bake for about 20 minutes covered with foil making sure it does not touch the casserole top. Then remove the foil and continue to bake for another 10 minutes until it is bubbling and browned nicely on top. If you want it more browned on top you can broil it on medium for 5 minutes uncovered.
Remove from the oven and let it rest for 10 minutes before serving garnished with a bit of fresh parsley and a slice of garlic bread on the side.