In a large skillet over medium-high heat, brown the ground beef and onions. About 5-7 minutes. Drain off excess fat and set it aside.
In a medium bowl, add milk, cream of mushroom soup, Worcestershire sauce, mustard, pepper, salt, and garlic powder. Mix until combined and set aside.
Spray your slow cooker with cooking spray. Then, place half the tater tots in the bottom of the slow cooker.
Evenly spread half of the ground beef over the tater tots. Then, sprinkle 1 cup of cheese over the ground beef. Next, layer corn and green beans. Top with remaining ground beef.
Place the remaining tater tops and cover with the sauce. Then, top with the remaining cheese.
Cover and cook on high for 3-4 hours or low for 7-8 hours.
Serve while hot and enjoy!