The Quaker Oats meatloaf recipe is an oldie but still a goodie.

2 lbs ground beef
1 cup tomato sauce or 1 cup ketchup or 1 cup salsa
3/4 cup Quaker Oats
1/2 cup chopped onion
1 large egg, beaten
1 tablespoon soy sauce or 1 tablespoon Worcestershire sauce
salt and pepper
Directions:

Preheat oven to 350°F. mix all ingreds, put in loaf pan and bake 1
hour. drain off fat.

I make my own variation of this, including adding 6 oz of cheddar
cheese, which I cut into 1/2 inch cubes and insert into the middle of
the loaf; shredded cheese melts too quickly and runs out, but if you
cube it, the cheese won't run out. I also dice 1/2 cup green pepper
or mix in a little can of those diced green chilies. I use V8 in to
mix in, and spread ketchup on top, because meatloaf has to have that
ketchup on top. I usually double the recipe, and put a rack on top of
the cookie sheet and put the loaf on top of the rack to drain the fat
as it cooks; I don't use a loaf pan because the meatloaf swims in the
fat.