The brothers were all educated at Newington College (1984–1991),[2] and took up rowing coached by Olympian and fellow Old Newingtonian Michael Morgan and deputy headmaster Robert Buntine.

Stewart's first state representative selection for New South Wales came in 1992 in the youth eight who contested and won the Noel F Wilkinson Trophy at the Interstate Regatta within the Australian Rowing Championships[4] From 1994 to 2004 he rowed in eleven consecutive New South Wales men's senior eights competing for the King's Cup at the Interstate Regatta.

He stroked the 2002 eight and only the 2004 crew was victorious, with the Stewart brothers suffering a long period of Victorian King's Cup dominance.

[5] Geoffrey made his Australian representative debut in 1994 competing at the World Rowing U23 Championships in Paris in a coxless pair with his twin brother James.

[3] Their 1997 season also included a campaign at the Henley Royal Regatta where as an Australian Institute of Sport crew they contested and won the 1997 Grand Challenge Cup.

[3] In 1998 Australia's Oarsome Foursome were in their first year of a post-Olympic comeback and they raced in various coxed combinations at the 1998 World Rowing Championships in Cologne.

In the final they met the British four of Cracknell, Pinsent, Redgrave and Ed Coode who foreshadowed what was planned for the Olympic Games and took the gold with Geoff Stewart and the Australians winning silver.