Brown the ground beef and onion together in a skillet, drain and put in the bottom of large rectangular casserole dish. Drain the liquid from the green beans and place on top of ground beef. Combine soups and pour on top of the green beans. Place the Tater tots on top and bake for 30-45 minutes in a 350°F oven. I serve this with a big green salad and a loaf of French bread.