Preheat your oven to 350°F (175°C).
In a large skillet over medium heat, brown the ground beef, breaking it apart with a wooden spoon until fully cooked. Drain excess fat if necessary.
Add chopped onion to the skillet and sauté until softened, approximately 3-4 minutes.
Stir in the garlic powder, onion powder, salt, and black pepper. Mix well.
In a mixing bowl, combine the uncooked rice, beef broth, cream of mushroom soup, and optional frozen mixed vegetables. Stir until everything is well mixed.
Combine the beef and rice mixture in the skillet, stirring until well combined.
Transfer the mixture to a greased 9x13 inch baking dish and spread it evenly.
Cover the dish with aluminum foil and bake in the preheated oven for 25 minutes.
After 25 minutes, remove the foil and sprinkle the shredded cheddar cheese over the top of the casserole. Bake uncovered for an additional 5 minutes, or until the cheese is melted and bubbly.
Allow the casserole to cool for a few minutes before serving.