Bake pasta to al dente, 1-2 minutes less than the minimum baking time
Drain noodles in a colander and rinse well with cold water
Brown Italian sausage and ground beef in one pan
Drain meat over an empty bowl to get the fat off of the meat
In the empty meat pan, brown onions and peppers in butter
Combine cooked noodles, spaghetti sauce, meat and vegetables in a large mixing bowl
Dice all but 10 pepperoni and add to above mixture
Pour mixture into greased 9x13 dish
Sprinkle cheese on top of casserole
Top with remaining pepperoni
Bake at 350 degrees uncovered for 25-30 minutes