Preheat your oven to 350°F (175°C).
In a large mixing bowl, combine the cooked chicken, uncooked rice, chicken broth, cream of mushroom soup, mixed vegetables, chopped onion, minced garlic, salt, black pepper, garlic powder, and onion powder. Mix well until all ingredients are combined.
Pour the mixture into a greased 9x13-inch baking dish and spread it out evenly.
Cover the dish with aluminum foil to prevent the top from burning.
Bake in the preheated oven for 30 minutes.
After 30 minutes, remove the foil and stir the casserole gently to combine. Sprinkle the shredded cheddar cheese evenly over the top.
Return the dish to the oven, uncovered, and bake for an additional 15 minutes, or until the cheese is melted, bubbly, and golden brown.
Once cooked, let it cool for a few minutes before serving. Garnish with chopped parsley if desired.