Oatmeal is a filler that works just like breadcrumbs in meatloaf! It provides structure, so the meatloaf doesn’t fall apart when cooking or slicing! Fillers like oatmeal or breadcrumbs also help to keep the meat tender and moist so it doesn’t have the firm texture of a hamburger, for example! Something else I love about oats is that it makes the meatloaf gluten-free for those who can’t eat gluten!