Begin by chopping the onion and green bell pepper into small, bite-sized pieces.

In a skillet over medium heat, brown the ground beef until it loses its pink color and drain excess fat.

In the slow cooker, add the cooked ground beef, chopped onion, chopped bell pepper, ketchup, Worcestershire sauce, brown sugar, garlic powder, mustard, and season with salt and pepper.

Stir everything together until all ingredients are evenly distributed.

Cover the slow cooker and set it to cook on low for about 4-6 hours, or on high for about 2-3 hours.

Once the cooking time is up, stir the mixture and adjust seasoning if needed, then serve in hamburger buns and garnish with toppings of choice.