01 - Preheat oven to 375°F. Lightly grease a 9x13-inch baking dish with cooking spray or butter.
02 - In a large skillet over medium heat, cook ground beef and chopped onion until beef is browned and onion is soft, about 6-8 minutes. Drain excess fat from the skillet.
03 - Stir in mixed vegetables, cream of mushroom soup, milk, ketchup, Worcestershire sauce, garlic powder, onion powder, salt, and black pepper. Simmer for 2-3 minutes until well combined and heated through.
04 - Spread the beef mixture evenly in the prepared baking dish. Sprinkle 1 cup of cheddar cheese over the top of the mixture.
05 - Arrange frozen tater tots in a single layer over the cheese and beef mixture, covering the surface completely.
06 - Bake uncovered for 35-40 minutes, until tater tots are golden brown and crispy.
07 - Remove from oven and sprinkle remaining cheddar cheese over the casserole. Return to oven for 5 minutes, until cheese is melted and bubbly.
08 - Let the casserole rest for 5 minutes before serving to allow the filling to set slightly.