Preheat the oven to 375°F (190°C).
In a large skillet, heat the olive oil over medium heat. Add the diced chicken and season with chili powder, cumin, garlic powder, salt, and pepper. Cook for about 5-7 minutes until the chicken is browned and cooked through.
Add the sliced onion and bell peppers to the skillet. Sauté for an additional 5 minutes until the vegetables are softened.
In a large mixing bowl, combine the cooked chicken and vegetables with black beans, corn, salsa, and cooked rice. Stir until well combined.
Pour the mixture into a greased 9x13 inch baking dish. Spread it evenly across the dish.
Top the casserole with shredded cheddar cheese, distributing it evenly over the top.
Cover the dish with aluminum foil and bake in the preheated oven for 20 minutes.
After 20 minutes, remove the foil and bake for an additional 10 minutes or until the cheese is melted and bubbly.
Remove from the oven and let it sit for a few minutes before serving.