Preheat oven to 350°F. Lightly grease 13x9 baking dish with non-stick spray; set aside.
Cook and drain the spaghetti according to the package instructions for “al dente.” While the water is boiling for the spaghetti, prepare the sauce.
In a large skillet, cook the ground beef, onion, bell pepper and garlic until the beef is browned and the vegetables are softened, about 7 minutes.
Stir in mushrooms, tomatoes, spaghetti sauce and seasoning salt. Season to taste with additional salt and pepper as needed.
Add drained pasta, beaten eggs and parmesan cheese, stirring to combine.
Add half the spaghetti mixture to baking dish. Sprinkle with 1 cup shredded mozzarella. Top with remaining half of spaghetti, remaining cup of mozzarella and cheddar cheese.
Cover with foil and bake for 25 minutes. Remove foil and bake for an additional 15 minutes, or until cheese is bubbly and beginning to brown.
Let rest for 5-10 minutes before slicing to serve.
Notes
You can substitute tomato sauce for the spaghetti sauce. Add 1 tablespoon of Italian seasoning or season to your taste.