In a medium bowl, combine eggs, milk, ketchup, breadcrumbs, and onion soup mix. Mix well with a spoon.
Add ground beef to mixture. Using clean hands, gently combine until just mixed - don't overmix.
Shape mixture into a loaf and place in slow cooker.
Cover and cook on LOW for 5 hours.
Carefully spoon off excess fat from around meatloaf.
Let rest 10 minutes before slicing.