This is from my Mom's recipe box, but I've made it many many times over the years.
1 1/2 # ground meat
1 can cream of chicken soup
onion, chopped
1 frozen pkg. mixed vegetables
Fry ground beef and onion together, after it is fried add a can of soup. Put in the bottom of 3 1/2 qt. casserole. Next layer, add vegetables, on top of vegetables add the tater tots. Bake at 375° for 1 hr.