Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, black beans, corn, diced tomatoes, cooked quinoa or rice, chili powder, cumin, garlic powder, onion powder, and half of the shredded cheddar cheese. Mix well until all ingredients are evenly combined.
Season the mixture with salt and pepper to taste.
Pour the mixture into a greased 9x13 inch baking dish and spread it evenly.
Top the casserole with the remaining cheddar cheese and pour the salsa over the top.
Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes.
Remove the foil and bake for an additional 10-15 minutes, or until the cheese is melted and bubbly.
Let the casserole cool for a few minutes before serving. Garnish with fresh cilantro if desired.