Tater Tot Casserole

1 pound ground beef
1 onion, chopped
Salt and pepper to taste
1/2 package (32 ounces) tater tots
1 can (10.75 ounce) condensed cream of mushroom soup
1/2 cup milk
1 1/2 cups shredded cheddar cheese

In a large skillet brown ground beef and onions. Drain excess fat and season with salt and pepper. Spread beef mixture evenly on the bottom of a 2 quart casserole dish. Arrange tater tots evenly over beef layer. In a small bowl, stir the soup into the milk until smooth; pour over tater tot and beef layers. Sprinkle cheddar cheese evenly over top. Bake in a preheated 350 degree oven for 30 to 40 minutes, until cheese is bubbly and slightly brown on top.