Gerard was a local Parramatta junior and began his career as a with the team in 1974 and, in a disappointing side that only just avoided a third wooden spoon in five years, won the club's rookie of the year award. Gerard soon shifted to the forwards and his game developed rapidly as the Eels advanced to the 1975 NSWRFL season's finals, and then the Grand Final in 1976. Gerard scored a try in that match but Eadie’s wonderful goal-kicking gave Manly-Warringah a narrow win. The following year, Gerard played strongly throughout, and the Eels won the minor premiershipfor the first time. An aggressive and powerful St. George forward pack, however, was far too much in the replay. 1978 saw Gerard begin the most productive period of his career, winning Rugby League Week’s ‘Player of the Year’ award and being selected for the 1978 Kangaroo tour despite not having played for New South Wales. He played in all five Tests in the second row, but did not represent Australia again until 1983. He is listed on the Australian Players Register as Kangaroo No. 518.
Manly-Warringah
In 1981 Gerard shifted to the Manly-Warringah Sea Eagles and his move to the front row was widely criticised at the time, but he did so well in that role that he was close to selection for his second Kangaroo tour in 1982 despite a below-par performance in the Grand Final. Ultimately he was not selected to tour, but did play one final Test against New Zealand the following year – besides playing in two Grand Final losses to his former club Parramatta.
Penrith
In 1985 he shifted to the Penrith Panthers and also played for Hull F.C. in 1986–87. Often used as a "fresh reserve" after the NSWRL allowed them for the first time, continued to play until 1989. During that year, he re-established himself as a regular member of Penrith’s starting pack, and surpassed Bob O'Reilly’s first grade record to become the first player to pass the 300 mark.
Milestones in 1989
surpassed Bob O'Reilly’s record number of first grade games
surpassed Max Krilich’s record number of games in all grades
became the first player ever to play 300 first grade games
Post-playing
In the late 1970s, Gerard was the editor of a rugby league publication called Rugby Leaguer which was a rival publication to the Big League magazine. In 1990 Gerard took over as coach of Penrith’s reserve grade side. Despite taking them to the finals for two seasons, he moved to the Metropolitan Cup for 1992 and his time coaching Parramatta’s reserves in 1994and 1995 was disastrous. In 1998 he joined the NSW state selection panel. Since 2002 the "Geoff Gerard Coach's Award" has been given to the Parramatta Eels' Premier Leagueplayer of the year.