In a highly decorated football career Gary played over 360 senior games. Starting in Shepparton, he played 73 games between 1978-8. He moved to Tasmania in 1982 and played 99 games from 1982 – 1986 for the New Norfolk Football Club. During this period he was part of the winning combination that the Eagles fielded to win the 1982 TFL premiership under Robbie Dykes.
		This team was famous for the fact it contained four sets of brothers; Graeme and Michael Hunnibell , Graeme and Wayne Fox, Ian and Gary Williamson, and Neville and Rodney Hill. Winners are grinners; the 1982 New Norfolk team celebrates their victory. Gary Williamson is fourth from left.
		The 1982 New Norfolk Premiership team. Pictured are Wayne Fox; fifth from left in the second row and next to him sixth from left is Graham Hunnibell . Also pictured are Gary Williamson; second from left in the front row, fourth from left is Michael Hunnibell and third from right is Hedley Thompson. Next to him; fourth from left is Robert Dykes .
		He transferred to the Clarence Football Club in 1987 and played 96 games for them until 1991. During this period he was selected to represent Tasmania 10 times and also represented the T.F.L. in intrastate matches 4 times. He won the club Best and Fairest in 1988 & 1991 and was Runner Up in 1988 & 1990. The year of 1991 was particularly memorable for Gary because he also won Tasmanian football's highest honour - the William Leitch Medal  and was made a Life Member of the Tasmanian Football League.
		Gary retired from statewide football at the end of the season and was hired as Captain/Coach of the Lindisfarne Football Club in 1992. The club achieved the distinction of playing in the Amateurs Grand Final but sadly were Runners Up. Gary decided to try his luck in the Huon Football Association the next year and from 1993 – 1995 coached the Cygnet Football Club to a premiership in 1994. He won the Ivan Short League Medal in 1993 and 1994 and he also won the club medal for Best and Fairest in 1993 and 1994 and was Runner Up in 1995.

When the SFL started in 1996 Gary moved to Hobart to coach then TFL side Hobart Football Club from 1996 – 1997 and the Sorell Football Club from 1998 - 1999.
During 2000 he was appointed General Manager of the Sorell Football Club.

Gary was also Media Liaison officer for the Southern Football League for two years during 2000 and 2001.

Gary was appointed as coach of SFL Regional League club Cygnet for the 2002 season and won the Regional League Premiership beating Lauderdale easily.

The General overseeing the troops in the 2002 SFL Regional League Grand Final.