1. Preheat the oven to 400°.
2. Combine first 7 ingredients in a large bowl. Add beef; mix gently to combine. With moist hands, shape beef mixture into 20 (1 1/2-inch) meatballs.
3. Heat a large cast-iron skillet over medium-high heat. Add half of the meatballs to pan; cook 4 minutes, turning to brown meatballs on all sides. Arrange browned meatballs in a single layer on a jelly-roll pan coated with cooking spray. Repeat procedure with remaining meatballs. Bake meatballs at 400° for 7 minutes or until done.