Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the shredded chicken, uncooked rice, chicken broth, cream of chicken soup, frozen mixed vegetables, garlic powder, onion powder, black pepper, and salt. Mix well until all ingredients are evenly combined.
Grease a 9x13-inch baking dish with olive oil. Pour the chicken and rice mixture into the dish, spreading it evenly.
Sprinkle the shredded cheddar cheese on top of the mixture. If using breadcrumbs, sprinkle them over the cheese for added crunch.
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 15-20 minutes, or until the cheese is bubbly and the rice is fully cooked.
Let the casserole cool for 5-10 minutes before serving.