In a skillet over medium heat, brown the ground beef or turkey until fully cooked. Drain excess fat if necessary.
Transfer the cooked meat to the slow cooker. Add the diced onion, bell pepper, minced garlic, black beans, kidney beans, corn, diced tomatoes, tomato sauce, taco seasoning, and broth. Stir to combine.
Season with salt and pepper to taste.
Cover and cook on low for 6-8 hours or on high for 3-4 hours.
Before serving, taste and adjust seasoning if needed. Serve hot with optional toppings as desired.