In a skillet over medium heat, brown the ground beef until fully cooked, breaking it apart with a wooden spoon. Drain excess fat and transfer the meat to the slow cooker.
In the same skillet, add the chopped onion, garlic, and bell pepper. Sauté for about 5 minutes or until the vegetables are softened. Transfer the mixture to the slow cooker.
To the slow cooker, add the kidney beans, black beans, crushed tomatoes, chili powder, cumin, oregano, salt, black pepper, and beef broth. Stir until all ingredients are well combined.
Set the slow cooker to low and cook for 6 hours. If using high heat, cook for 3-4 hours.
Once the cooking time is up, taste and adjust seasoning if necessary.
Serve hot with optional toppings if desired.