Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish with cooking spray or butter.
In a large mixing bowl, combine the cooked rice, broccoli florets, 3/4 cup of the cheddar cheese, cream of mushroom soup, milk, garlic powder, onion powder, black pepper, and salt. Mix until well combined.
Pour the mixture into the prepared baking dish and spread it evenly.
If using breadcrumbs, mix them with the melted butter in a small bowl, then sprinkle the mixture evenly over the casserole.
Top the casserole with the remaining 1/4 cup of cheddar cheese.
Bake in the preheated oven for 25-30 minutes, or until the casserole is bubbly and the cheese is melted and golden.
Remove from the oven and let it cool for about 5 minutes before serving.