Preheat oven to 350° F (180° C). Combine Knorr® Recipe Onion Soup Mix, ground beef, bread crumbs, eggs and 1/2 cup (125 mL) ketchup in large bowl. Shape into loaf in 13 x 9-inch (3.5 L) baking or roasting pan or on rimmed baking sheet.
Bake uncovered 40 minutes. Meanwhile, combine remaining 1/2 cup (125 mL) ketchup and vinegar in medium bowl.
Spread ketchup mixture evenly over meatloaf and continue baking 20 minutes, or until done. Let stand 10 minutes before serving.