In a large skillet, heat a tablespoon of olive oil over medium heat. Add the chopped onion and garlic; sauté until softened, about 3-4 minutes.
Add the ground turkey (or beef) to the skillet, breaking it apart with a spoon. Cook until browned and cooked through, about 6-8 minutes.
Stir in the diced bell peppers, cooked brown rice, black beans, diced tomatoes (with their juices), corn, chili powder, cumin, smoked paprika, salt, and pepper. Mix well and allow the mixture to cook for another 5 minutes, letting the flavors meld.
Transfer the mixture to a lightly greased 9x13 inch baking dish, spreading it out evenly.
Sprinkle the shredded cheese over the top of the casserole.
Cover with aluminum foil and bake in the preheated oven for 25 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and lightly golden.
Allow it to cool for a few minutes before serving.
Notes
Serve warm directly from the baking dish, garnished with fresh cilantro or parsley for a pop of color and freshness.