Meatloaf is an American classic, and most recipes include a filler such as bread or cereals, which likely originated during lean times in the U.S. economy as a way to stretch expensive meat with cheap grains. However, fillers are also essential to add structure and moisture to meatloaf, and this one ingredient works better than any other.

Putting rolled oats in your meatloaf sounds strange, but recipes from The Spruce Eats, Epicurious, and more add oats to the ground meat mixture for a moister and juicer result. Oats bind the meatloaf mixture together, but don't suck up moisture and dry the loaf out in the way that breadcrumbs or soaked bread can.

Also, oats are a great option if you're dining gluten-free, since many brands do not contain gluten. Because meatloaf doesn't have a very long cooking time, The Kitchn recommends using quick-cooking rolled oats, which cook faster; with this secret ingredient in hand, all that's left to do is perfect the ketchup glaze on your nice and moist meatloaf.