Preheat Oven: Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with non stick cooking spray.
Cook Rice and Chicken: Prepare the rice according to package instructions. Cook the chicken by boiling, baking, or using rotisserie chicken for convenience.
Steam Broccoli: If using fresh broccoli, steam it until tender but still crisp. If using frozen broccoli, thaw and drain excess water.
Mix Ingredients: In a large mixing bowl, combine cooked rice, shredded chicken, broccoli, cheddar cheese, cream of chicken soup, milk, sour cream, garlic powder, onion powder, salt, and pepper. Mix until well combined.
Assemble Casserole: Transfer the mixture to the prepared baking dish and spread it evenly.
Optional Topping: If using a breadcrumb topping, mix panko breadcrumbs with melted butter and sprinkle evenly over the casserole.
Bake: Bake in the preheated oven for 25-30 minutes or until the casserole is hot and bubbly. If using breadcrumbs, they should be golden brown.
Serve: Let the casserole sit for 5 minutes before serving. Enjoy it as a standalone meal or pair it with a fresh side salad.