In a large skillet over medium-high heat, cook the beef, onion, bell pepper, and garlic until beef is browned, about 6 minutes. Drain the beef mixture if your meat is very greasy.

Transfer the browned beef mixture to a 6-quart slow cooker, and add the beans, diced tomatoes, tomato sauce, broth, chili powder, cumin, oregano, salt, and pepper. Stir well.

Cover and cook on high for 3 to 4 hours or on low for 6 to 8 hours. Serve topped with sour cream, cheese, and green onions or any desired toppings.