Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine the cooked rice, shredded chicken, broccoli florets, cream of chicken soup, milk, garlic powder, onion powder, salt, and pepper.
Transfer the mixture into a greased 9x13 inch baking dish.
Sprinkle the shredded cheddar cheese over the top of the casserole.
Cover the baking dish with aluminum foil and bake for 30 minutes.
Remove the foil and bake for an additional 10-15 minutes until the cheese is bubbly and golden.
Let the casserole cool for a few minutes before serving.