Preheat the Oven:
Preheat your oven to 375°F (190°C) and grease a 9×13-inch baking dish.

Cook the Ground Beef:
In a large skillet, cook the ground beef over medium heat, breaking it apart as it cooks. Drain any excess fat.

Sauté the Onion:
Add the chopped onion to the skillet with the beef and cook for 2-3 minutes until softened.

Make the Creamy Beef Mixture:
Stir in the cream of mushroom soup and milk, seasoning with salt and pepper. Simmer for 5 minutes, stirring occasionally.

Assemble the Casserole:
Spread the beef mixture evenly in the prepared baking dish. Layer the frozen tater tots evenly over the top.

Bake the Casserole:
Bake for 25-30 minutes, or until the tater tots are golden brown and crispy.

Add Cheese and Final Bake:
Sprinkle the shredded cheddar cheese on top and bake for an additional 5 minutes until the cheese is melted.

Serve and Enjoy:
Let the casserole cool for a few minutes before serving. Enjoy the hearty, delicious goodness!