In round 2 of the 2018 Super Rugby season, McDermott made his debut off the bench for the Queensland Reds.
McDermott has since had a stellar 2020 campaign with the Queensland Reds in Super Rugby AU starting all nine matches played and scoring 10 points.
He played all games in the 2021 France rugby union tour of Australia, starting in one game and coming off the bench for the rest, and scoring his maiden try in the deciding test, won 33-30 and confirming the Trophee des Bicentenaries would remain with Australia.
McDermott also appeared in the 2021 Bledisloe Cup series, where the Wallabies lost both games at Eden Park in Auckland.
He would play a pivotal role in the Wallabies' wins against the Springboks and the Pumas, but was replaced by fellow halfback Nic White in a test against Argentina, forcing him to be benched, and dropped all-together in the final test against Los Pumas, being replaced by Jake Gordon.