Fold two long strips of heavy-duty foil into a cross-shaped sling in a 6-quart crockpot and coat it lightly with oil.
Soak the breadcrumbs in the milk for 5 minutes, then add the beef, eggs, onion, Worcestershire, salt, pepper and 1/4 cup ketchup and mix gently.
Shape the mixture into a compact 9-by-5-inch loaf on the foil sling.
Mix the remaining ketchup with the brown sugar and vinegar, spread it over the loaf, and cook covered on low for 4 to 4 1/2 hours until the center reaches 160°F.
Use the sling to move the loaf to a board, rest for 15 minutes, and slice into 10 portions.