Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, black beans, corn, diced tomatoes, cooked brown rice, chili powder, cumin, garlic powder, onion powder, salt, and black pepper. Mix well until all ingredients are evenly combined.
Transfer the mixture to a greased 9x13-inch baking dish, spreading it out evenly.
Sprinkle the shredded cheddar cheese over the top of the casserole.
Bake in the preheated oven for 25-30 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it cool for 5 minutes. Garnish with chopped cilantro if desired.
Serve warm with diced avocado and lime wedges on the side.