Preheat the oven to 450˚ F. Line 2 baking sheets with foil and coat with cooking spray.
Combine the beef, breadcrumbs, milk, eggs, onion, garlic, parsley, 2 teaspoons salt and 1/2 teaspoon pepper in a large bowl; mix with your hands until combined. Form into 1 1/2-inch meatballs (about 30). Arrange the meatballs on the prepared baking sheets.
Bake the meatballs until browned and cooked through, 12 to 15 minutes.