In a large pan over medium high heat brown ground beef and sausage. Drain excess fat if necessary.
Add onions, bell pepper, mushrooms and garlic and saute' for 5 minutes.
Add spaghetti sauce and let simmer for 30 minutes.
Add approx. 1/3 of the sauce to the bottom of a 9 x 13 casserole dish.
Add half of the par cooked spaghetti.
Add another 1/3 of the sauce to the top of the spaghetti.
Top the spaghetti with 1/2 of the cheeses.
Followed by the remaining sauce.
Followed by the remaining cheeses.
Bake in a pre-heated 350º oven for 30 minutes or until bubbly and golden brown.
Let rest 10-15 minutes to firm up before serving.