 Coulson captained the Scarborough under-19 team that won the Northern Alliance League title in the 2003–04 season.He made his first-team debut as a 16-year-old after coming on as a 79th-minute substitute at home to Accrington Stanley in a 4–0 Conference National victory on 23 October 2004, making him the second youngest player in Scarborough's history.Coulson became Scarborough's youngest goalscorer after he scored an equalising goal against Tamworth in a 2–2 home draw on 15 March 2005 with 10 minutes of the match remaining.