01 - Preheat the oven to 375°F. Grease a 9x13-inch baking dish with cooking spray or butter.
02 - In a large skillet over medium heat, cook the ground beef and chopped onion until the beef is browned and the onion is soft, about 6–8 minutes. Drain excess fat from the skillet.
03 - Stir in the corn, peas (if using), cream of mushroom soup, sour cream, 1 cup of cheddar cheese, milk, Worcestershire sauce, salt, and pepper. Mix until well combined and heated through.
04 - Spread the beef mixture evenly in the prepared baking dish. Arrange the frozen tater tots in a single, even layer over the beef mixture.
05 - Bake for 35 minutes, then sprinkle the remaining 1/2 cup cheddar cheese over the top. Return to the oven and bake for 10 more minutes, or until the cheese is melted and the tater tots are golden brown and crispy.
06 - Remove from the oven and let rest for 5 minutes before serving. Garnish with chopped parsley if desired.