In a skillet over medium heat, brown the ground turkey or beef until it's no longer pink. Season with salt and pepper. Drain any excess fat.
Transfer the cooked meat to the slow cooker.
Add the black beans, corn, diced tomatoes with green chilies, taco seasoning, cooked rice, salsa, diced bell peppers, and diced onion to the slow cooker.
Stir all the ingredients together until well combined.
Cover the slow cooker and cook on low for 4-6 hours or on high for 2-3 hours.
About 20 minutes before serving, sprinkle the shredded cheddar cheese on top of the casserole and cover until melted.
Once the cheese is melted and bubbly, give the casserole a gentle stir before serving.
Notes
Serve directly from the slow cooker, garnished with dollops of sour cream, slices of avocado, and a sprinkle of fresh cilantro on top for a burst of color and freshness.