In 2006 he competed in Formula Three Euro Series where he finished 3rd at Spa, 2nd at LeMans, and won the final Hockenheim race.

In 2007 he made starts in the A1 Grand Prix series for A1 Team USA and took second in the feature race at Autódromo Hermanos Rodríguez in Mexico City.

He later switched teams and returned to Newman Wachs Racing after Genoa shut down and finished in a first-place tie to teammate John Edwards, but lost the tiebreaker.

After two years on the sidelines, Summerton was signed to Rahal Letterman Lanigan Racing for the 2012 12 Hours of Sebring along with fellow BMW drivers Joey Hand and Dirk Müller in the GTLM class.

Summerton set fastest race laps at 2 events along with finishing at Petit LeMans 3rd place.