Lowe joined the Quins Academy Professionals in summer 2008, after leaving Epsom College, where he played in their first XV.
He represented Surrey U18s, and also played for Harlequins in the A league whilst still a schoolboy. Lowe was called up to the England U20s squad for the U20 Six Nations, where he was in fine try-scoring form, and continued to represent England U20s throughout the Junior World Championship in the summer of 2009.
An impressive 2010/11 season saw him help Quins claim the Amlin Challenge Cup and get shortlisted for the Land Rover Discovery of the Season. In the 2011/12 season, Lowe was a key part of the Harlequins team which won the Aviva Premiership for the first time in their history. Lowe started the final against Leicester Tigers, helping Harlequins to a 33-23 win. His efforts throughout the season saw him get included in Stuart Lancaster's England squad for the 2012 Summer tour to South Africa. In the summer of 2012, his body nutrition shakes, "Lowetein", was released.