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 softened, about 6–8 minutes. Drain excess fat from the skillet.
03 - Sprinkle garlic powder, onion powder, salt, and black pepper over the beef mixture. Stir well to distribute the seasonings evenly.
04 - Pour the condensed cream of mushroom soup and milk into the skillet. Stir until fully combined and the mixture forms a uniform sauce. Add frozen corn and frozen peas if using, and mix well.
05 - Transfer the beef and vegetable mixture into the prepared baking dish, spreading it into an even layer. Sprinkle the shredded cheddar cheese generously over the top.
06 - Place frozen tater tots in a single, even layer across the entire surface of the casserole. Arrange them close together for maximum coverage.
07 - Bake uncovered for 40–45 minutes until tater tots are golden brown and crispy, and the edges are bubbling.
08 - Remove from oven and let the casserole rest for 5 minutes before serving. This allows the layers to set and makes serving easier.