In the post war years, the club continued to play at Shirehaugh. However, the conditions at the ground started to gradually get worse, and the team led by Bill Caird look at other options into where the club could play.
In 1948, the club applied for full membership of the Scottish Rugby Union, which was accepted in May of that year, with the club proposed by Melrose RFC and seconded by Stewart's Rugby Club to join. Musselburgh became the 56th full member of the Union as a result.
On the playing front, the club's most notable performances came on the Sevens Circuit, including winning the Murrayfield Sevens in 1949.