Magill competed in the Indianapolis 500 three times, with his first start coming in 1957. The next year, when racing legend Juan Manuel Fangio was unable to compete due to a contractual conflict, Magill drove the car in which Fangio had been practicing. He was involved in an accident in the first lap of the race but, after over an hour in the pits, he returned to the track to finish 17th. He drove in his final 500 in 1959, when he was eliminated from the race in a four-car accident.