Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking dish with olive oil.
In a large bowl, combine the cooked chicken, steamed broccoli, uncooked rice, cream of chicken soup, chicken broth, garlic powder, onion powder, salt, and pepper. Mix well until all ingredients are evenly coated.
Pour the mixture into the prepared baking dish, spreading it out evenly.
Sprinkle the shredded cheddar cheese on top of the mixture. If using, add breadcrumbs for a crunchy topping.
Cover the dish with aluminum foil and bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil and bake for an additional 15-20 minutes, or until the cheese is bubbly and the rice is tender.
Let the casserole cool for 5-10 minutes before serving.