Taken straight to the front by jockey Jim Byrne, Apache Chase ($12) held firm up the Eagle Farm straight to claim the 1300m race on Saturday by a short-head from Paulele ($6) with Eleven Eleven ($15) a head away third.
A long-time friend of Peter Moody, Forster had Black Caviar housed at her stables when the unbeaten mare campaigned in Brisbane.
Prior to Saturday's success, Forster had started 22 runners at Group 1 level for two placings, both with I'm Belucci during the 2015/16 seasons.
Apache Chase entered Saturday's race coming off a second-place finish in the inaugural staging of The Archer (1300m) at Rockhampton on May 7.
"All I said to J Byrne was 'don't go slow', use his speed, use his gate, dig him and send him, get to the three (300m) and let him go," Forster said.
"If they are good enough to run past him, they are good enough, but if they are not, too bad.
"They weren't a hope, they just left him in front, and he just walked."
Forster has always held Apache Chase in high esteem and held out hopes the gelding could provide her with that elusive Group 1 win.
Apache Chase contested The Golden Eagle at Rosehill last before setting her sights on the Brisbane Winter Carnival and was especially thankful of owner Mike Sherrin.
"He's sitting in my office having a drink I suppose, watching on his own in the office," Forster said.
"They've been so good to me. They've trusted me with this horse.
"We could have sold this horse 18 months ago. Mike said, 'do you think he can win a Group 1?', I said 'yeah'. I said to J Byrne 'can we win a Group 1', he said, 'can I ride', I said 'yeah', and he said, 'we can win a Group 1'."