Preheat your oven to 350°F (175°C).
In a large bowl, combine the cooked rice, broccoli florets, and cream of mushroom soup.
Add mayonnaise, garlic powder, and half of the cheddar cheese to the mixture.
Season with salt and pepper, then stir until well combined.
Transfer the mixture into a greased baking dish, spreading it evenly.
Sprinkle the remaining cheddar cheese over the top, followed by breadcrumbs.
Bake in the preheated oven for 30-35 minutes until bubbly and golden brown.
Let the casserole cool for a few minutes before serving.
