Grandma's Golden Nugget Meatballs

1 1/2 lb ground beef
1 1/2 c soft bread crumbs
1/3 c chopped green peppers
1/2 tsp dry mustard powder
1/2 tsp garlic salt
2 sm cans tomato sauce
1/8 tsp pepper
1 tsp salt
1 egg
1/3 c catsup
16 cubes of cheese

Serve over cooked spaghetti or rice.