Saute onion on medium-low heat first to soften it up. Combine ground beef, rolled oats, onion, milk, egg (if using), Worcestershire sauce, salt, pepper, mixing thoroughly with hands. Form meat into balls and place on large greased cookie sheet. Bake in 350 °F oven for about 25 minutes or until browned.
With slotted spoon, transfer meatballs to trays, spacing balls so they are not touching. Let cool, then freeze until firm. Package in heavy plastic bags or other container and store in freezer.
Adapted from “The Canadian Living Cookbook”, (c) 1987
Omit Worcestershire sauce or use safe alternative to avoid corn and/or fish.