McGrath competed at the Junior World Championships in 2018 and 2019; he raced all of the events (DH, SG, AC, GS, and SL) both years. In 2018, he was the best U18 skier in three events; in 2019, he was the silver medalist in the combined. McGrath was also fourth in the downhill, just 0.01 second from the podium.