Heat olive oil in a large skillet over medium heat. Sauté diced onion for 3-4 minutes until translucent.
Add ground beef to the skillet, breaking it apart as it cooks. Stir until browned and fully cooked, then drain excess fat.
Add garlic powder, onion powder, salt, pepper, uncooked rice, beef broth, cream of mushroom soup, and mixed vegetables to the skillet. Mix well.
Bring the mixture to a boil, then reduce heat to low, cover, and simmer for 20-25 minutes until rice is tender.
Stir in half of the shredded cheddar cheese, then transfer the mixture to a baking dish. Sprinkle remaining cheese on top.
Preheat oven to 350°F. Bake casserole for 15-20 minutes until cheese is melted and bubbly. Let sit for 5 minutes before serving.