Heat oven to 375°F. In large bowl, mix together meat, onion, instant oatmeal, eggs, ketchup, milk, Worcestershire sauce, and salt until well-combined. Divide meat mixture into 8 servings and shape into individual loaves. Place meat loaves in a 9 x 13-inch baking pan.
In a small bowl, blend together ketchup and brown sugar. Brush tops and sides of meat loaves; bake 35 to 40 minutes, or until a meat thermometer registers 160°F when inserted into center of loaves. Let cool 10 minutes.
Serve 4 meat loaves with mashed potatoes, if desired. Cool remaining meat loaves for 25 minutes. Wrap individually in plastic wrap or waxed paper and freeze.
Place meat loaves in a pan, and thaw in refrigerator overnight. Unwrap and bake 15 minutes in 350°F oven, or microwave loaves just until heated through.