I usually double the following recipe:
1 and 1/2 lb. lean ground beef
3/4 cup quick oats
1/4 cup finely chopped onion
1/4 teaspoon black pepper
1 egg, slightly beaten
1 of 10.5 oz. size vegetable (ABC) soup
1/2 cup milk
(I usually don't add salt because it seems there is enough in the can of soup.)
Lightly, but thoroughly, mix the above ingredients together, pack lightly into a greased/sprayed loaf pan OR flatten out in a sprayed rectangular glass baking dish (double recipe needs 9x13" pan/dish). Spreading Ketchup on top of meat is optional.
I like to make a 'trench' between the edges of the meat and the dish so there's a place to collect any accumulating fat.
Bake loaf pan at 350-degrees for about 1 hour; or bake flat pan/dish for 40-45 minutes or until dark/rich brown. Since ovens vary, check before the time is up.