Mike O'Neill played in Widnes' 19-5 victory over Bradford Northern in the Premiership Final during the 1979–80 season at Station Road, Swinton on Saturday 17 May 1980, the 23-8 victory over Hull F.C. in the Premiership Final during the 1981–82 season at Headingley Rugby Stadium, Leeds on Saturday 15 May 1982, the 22-10 victory over Hull F.C. in the Premiership Final during the 1982–83 season at HeadingleyRugby Stadium, Leeds on Saturday 14 May 1983, the 38-14 victory over Hull F.C. in the Premiership Final during the 1987–88 season at Old Trafford, Manchester on Sunday 15 May 1988, the 18-10 victory over St. Helens in the Premiership Final during the 1988–89 season at Old Trafford, Manchester on Sunday 14 May 1989, and the 28-6 victory over Bradford Northern in the Premiership Final during the 1989–90 season at Old Trafford, Manchester on Sunday 13 May 1990.
Mike O'Neill played as an interchange/substitute in Widnes' 12-3 victory over Wakefield Trinity in the 1979 Challenge Cup Final during the 1978–79 season at Wembley Stadium, London on Saturday 5 May 1979, in front of a crowd of 94,218, played left-, i.e. number 8, the 18-9 victory over Hull Kingston Rovers in the 1981 Challenge Cup Final during the 1980–81 season at Wembley Stadium, London on Saturday 2 May 1981, in front of a crowd of 92,496, played left-, i.e. number 8, in the 14-14 draw with Hull F.C. in the 1982 Challenge Cup Final during the 1981–82 season at Wembley Stadium, London on Saturday 1 May 1982, in front of a crowd of 92,147, played left- in the 9-18 defeat by Hull F.C. in the 1982 Challenge Cup Final replay during the 1981–82 season at Elland Road, Leeds on Wednesday 19 May 1982, in front of a crowd of 41,171, and played right-, i.e. number 12, the 19-6 victory over Wigan in the 1984 Challenge Cup Final during the 1983–84 season at Wembley Stadium, London on Saturday 5 May 1984, in front of a crowd of 80,116, and was as an interchange/substitute, i.e. number 15, in Leeds' 16-26 defeat by Wigan in the 1994 Challenge Cup Final during the 1993–94 season at Wembley Stadium, London on Saturday 30 April 1994, in front of a crowd of 78,348, in doing so he set, and still holds, the record for the longest time span between first and last Challenge Cup Final appearances.
John Player/John Player Special Trophy Final appearances
Mike O'Neill played in Widnes' 20-14 victory over Wigan in the Charity Shield during the 1988–89 season at Okells Bowl, Douglas, Isle of Man on Sunday 21 August 1988, and the 27-22 victory over Wigan in the Charity Shield during the 1989–90 season at Anfield, Liverpool on Sunday 27 August 1989.