After successful spells with Ayr United and Queen of the South, John McCosh joined Exeter City in 1930 but only made one league appearance before signing for New Brighton.

John was with Auchinleck Talbot before joining Ayr United in 1925 where he helped the club win the Scottish League Second Division championship before moving to Cowdenbeath in 1928. He then spent 1929/30 with Queen of the South for the 1929/30, where he was leading scorer with eleven goals, before joining Exeter City in the summer of 1930. 

John played in the reserves during his time at St James’ Park and made a solitary league appearance for the first-team in the 7-2 defeat at Queen's Park Rangers in December 1930.