Preheat the oven to 350°F (175°C).
In a large mixing bowl, combine the cooked rice, diced chicken, cream of chicken soup, chicken broth, frozen vegetables, onion powder, garlic powder, salt, and pepper. Stir until well combined.
Carefully pour the mixture into a greased 9x13 inch baking dish.
Sprinkle shredded cheddar cheese evenly over the top of the chicken and rice mixture.
In a separate bowl, mix together the breadcrumbs and melted butter until the breadcrumbs are coated. Spread the breadcrumb mixture evenly over the cheese layer.
Cover the baking 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 minutes, or until the topping is golden brown and the casserole is bubbling.
Remove from the oven and let it sit for about 5 minutes before serving.