Combine all of the ingredients: In a large bowl, gently mix together all of the ingredients for the meatballs: ground beef, breadcrumbs, egg, onions, ketchup, Dijon, garlic, oregano, garlic powder, parsley, salt, and Worcestershire. Work the meat just until combined either with clean hands or a spatula or spoon.
1 lb. ground beef, 1/2 cup Italian breadcrumbs, 1/4 cup white onion, finely chopped or grated, 1 egg, 2 Tbsp. ketchup, 1 Tbsp. Dijon mustard, 2 cloves garlic, minced, 1 tsp. garlic powder, 1 tsp. dried parsley, 1 tsp. salt, 1/2 tsp. oregano, 2 tsp. Worcestershire