In a large bowl, combine the ground beef, oats, egg, minced onions, garlic, Worcestershire sauce, onion powder, and skim milk.
Mix gently until just combined.
Use a #40 scoop to portion and roll into meatballs (about 18–20 total).
Place the meatballs in the bottom of your crockpot.
In a separate bowl, whisk together the beef broth, gravy mix, Worcestershire sauce, garlic powder, and onion powder.
Pour the mixture over the meatballs.
Cover and cook on Low for 5–6 hours.
About 15 minutes before serving, gently stir in the evaporated milk.