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 thoroughly.
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 cheddar cheese over the mixture, ensuring even coverage.
05 - Arrange frozen tater tots in a single, even layer over the cheese and beef mixture. Place them closely together for maximum coverage.
06 - Bake uncovered for 35–40 minutes, until tater tots are golden brown and crispy, and the filling is bubbling around the edges.
07 - Remove from oven and sprinkle remaining 1 cup cheddar cheese evenly over the entire casserole. Return to oven for 5 minutes, until cheese is fully melted and slightly bubbling.
08 - Let the casserole rest for 5 minutes before serving. This allows the filling to set slightly and makes serving easier.