2 cups thinly sliced onions
2 cups chopped green bell peppers
1 can kidney beans, drained and mashed
1 can (8-oz) tomato sauce
2 garlic cloves, minced
2 tbsp ketchup
1 tablespoon prepared mustard
1 tsp chili powder
cider vinegar, optional
4 whole-grain sandwich rolls, split
Combine the onions, bell peppers, beans, tomato sauce, garlic, ketchup, mustard, and chili powder in a crockpot or slow cooker. Stir in the cider vinegar, if using. Place lid on cooker and cook approximately 5 hours on low setting.
Serve on the sandwich rolls with your favorite condiments such as lettuce leaves, sliced tomatoes, thin avocado slices, etc.