Hungry Mob Casserole

1 Pound of Bacon, Crisped and Chopped
1 Onion, Chopped and Sautéed in a little of the Bacon fat
2 Pounds Ground Round, Browned
2 Pounds Spaghetti, Cooked and Drained
1 Can Ripe Olives, Drained
2 Cans Mushrooms 
2 Cans Spaghetti Sauce
¼ Pound Grated Parmesan Cheese
¼ Pound Grated Cheddar Cheese

Mix all ingredients together except cheddar cheese. Top with cheddar and bake in 350 degree oven until cheese bubbles. Serves ten.