Preheat the oven to 375°F and lightly grease a 9x13-inch baking dish.
In a large mixing bowl, combine the cream of chicken soup and milk until smooth. Stir in the salt, black pepper, and garlic powder.
Add the shredded chicken, broccoli florets, cooked rice, and 1 cup of the cheddar cheese to the bowl. Mix until everything is evenly coated.
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 for 25 to 30 minutes, until the cheese is melted and the edges are lightly golden. Let it rest for 5 minutes before serving.