Preheat the oven to 375°F and lightly grease a 9x13 baking dish.
In a large mixing bowl, combine the cooked rice, shredded chicken, chopped broccoli, cream of chicken soup, milk, garlic powder, onion powder, salt, and pepper. Stir until everything is evenly coated.
Fold in 1 cup of the shredded cheddar cheese so it is distributed throughout the mixture.
Transfer the mixture to the prepared baking dish and spread it into an even layer.
Sprinkle the remaining 1/2 cup of cheddar cheese over the top.
Bake uncovered for 25 to 30 minutes until the cheese is melted and beginning to brown at the edges.
Remove from the oven and let the casserole rest for 5 minutes before serving.