Heat oven to 325°F.
Heat olive oil in medium-size skillet. Add onion; sauté 10 minutes or until very tender.
Combine beef, bread crumbs, eggs, milk, oregano, basil, garlic salt, seasoning salt, Worcestershire, pepper and onion in bowl; lightly mix with wooden spoon or hands until combined but not overmixed.
Shape beef mixture into 2-inch meatballs. Arrange in single layer, not touching each other, in 15 x 10 x 2-inch baking pan.
Bake, uncovered, in 325°F oven for 20 minutes.
Combine ketchup, barbecue sauce, brown sugar, vinegar and pinch garlic salt in small saucepan. Heat over medium heat just until simmering.
Remove meatballs from pan to paper towel to drain. Wipe out baking pan. Return meatballs to pan; cover with ketchup sauce. Cover pan tightly with aluminum foil.
Return baking pan to 325°F oven and bake for 20 minutes or until meatballs are no longer pink in center. (To keep meatballs warm up to a half-hour, decrease oven temperature to 200°F; place tightly covered pan in oven.)