He began to feature more for the first team towards the end of the 2007–08 season, with his first start coming against St Mirren at Tynecastle on 19 April 2008 scoring his first senior goal to put Hearts in front as Hearts came back from a goal down to win 3–2. This led to Glen being awarded the "Clydesdale Bank U19 Graduate award" for his breakthrough to the first team. He continued his form with the only goal of the game in his second start against Inverness Caledonian Thistle on 26 April. In April 2008 he signed a new four-year contract extending his stay until the summer of 2012.