It was the tenth running of the Australian Touring Car Championship and the first to be contested over a series of heats rather than as a single race.
It was Geoghegan's fifth and final Australian Touring Car Championship victory, creating a record that would not be equalled until 1989.
Beechey's car was repaired in time for the race and he took the lead off the start, only for Geoghegan to move past at the first corner.
Both drivers set a new lap record of 49.1 seconds before Geoghegan made a move for the lead at the end of the straight.
Bob Jane had qualified second but blew an engine on lap 9, while Norm Beechey did not even start the race after an accident in practice.
[2] Bob Jane took pole position for the Mallala round ahead of Ian Geoghegan and Allan Moffat.
Geoghegan assumed an eight-point lead in the championship over Hamilton, with Jane maintaining third place courtesy of his victory at Calder.
[2] Ian Geoghegan took his third pole position of the season ahead of Norm Beechey, whose time was equalled by Alan Hamilton.
Geoghegan moved into the lead at the start of the race and pulled away from Beechey, before hitting a dropped exhaust pipe on lap 8.
Beechey took his first win of the season, and the first championship race victory for Holden, with Hamilton again finishing in second place.
Geoghegan's troubles saw his championship lead drop to just three points over Hamilton, meaning that the title would be decided at the final round at Symmons Plains.
[2] Tyre punctures for Harvey on laps 15 and 16 forced him out of contention, leaving Beechey in the lead and Hamilton in second.
Beechey's consecutive wins in the final two rounds saw him take third place in the points standings ahead of McKeown and Peter Manton.