O'Toole made his debut for the New York Red Bulls II in the summer of 2016 at the age of 17. He scored his first professional goal on July 23 in a 3–2 loss to Charleston Battery.[2] On October 23, 2016, O'Toole helped the club to a 5–1 victory over Swope Park Rangers in the 2016 USL Cup Final, appearing as a starter in the cup final.[3]