Cowboy Pork and Beans

1 pound ground beef
2 medium onions, finely chopped
1 small green bell pepper, finely chopped
2 cups ketchup
1 teaspoon vinegar
1/4 cup brown sugar
2 teaspoons prepared mustard
2 (16 ounce) cans pork and beans
1 teaspoon salt
1 teaspoon black pepper

Brown ground beef, onions and bell pepper in a 10-inch skillet. Add remaining ingredients. Pour into baking dish and bake at 350 degrees F for 15 to 20 minutes or until mixture is bubbly.