[2] McCallion started his career with Huddersfield-based amateur club Moldgreen, and was selected for the 1983 BARLA Young Lions tour of New Zealand.
[5] McCallion played in all 37-matches in Halifax's victory in the Championship during the 1985–86 season, scoring 7-tries in 30 League matches and 2 in Cup competitions.
McCallion played hooker, and scored a try in Halifax's 19-18 victory over St. Helens in the 1987 Challenge Cup Final during the 1986–87 season at Wembley Stadium, London on Saturday 2 May 1987, and played hooker in the 12-32 defeat by Wigan in the 1988 Challenge Cup Final during the 1987–88 season at Wembley Stadium, London on Saturday 30 April 1988.
McCallion played hooker in Halifax' 12-24 defeat by Wigan in the 1989–90 Regal Trophy Final during the 1989–90 season at Headingley, Leeds on Saturday 13 January 1990.
[12] On 25 March 2004 six footballers were inducted into Rugby League Ireland's inaugural Hall of Fame at the Rugby League Heritage Centre in Huddersfield, they were; John "Jack" Daly (Huddersfield/Featherstone Rovers), Robert "Bob" Kelly (Keighley/Wakefield Trinity/Batley), Seamus McCallion (Halifax/Leeds/Bramley), Thomas "Tom" McKinney, (Salford/Warrington/St.