Trent Copeland decimated Bankstown's top order to put St George in a strong position after day one of their two-day, round two match on Saturday.
Saints captain Nick Stapleton won the toss and sent the hosts in to bat at Bankstown Oval, with St George making the most of the conditions.
Former Test quick Copeland was the standout, taking 5-21 from his 10 overs to have Bankstown struggling at 7-77 at stumps on day one.
Only 38 overs were possible due to the wet weather but Copeland made the most of his time in the middle, dismissing Bankstown's top four batsmen.
The NSW seamer bowled Daniel Solway (6) and Jake Fawcett (0) and had Peter Dignam (6) and Nick Carruthers (9) caught to have Bankstown reeling at 5-19.
Stapleton and Tom Ortiz also picked up a wicket each for St George.
Ben Taylor top scored for Bankstown with 34 as he led his side towards triple figures.
Ben Le Bas and Liam Marshall are the not out batsmen, with the pair to resume without scoring.
St George will want to seal victory when play restarts on day two as they look to kick start their season following their disappointing opening round defeat to Manly-Warringah.
In the lower grades, Bankstown have already secured first innings points in second grade after rolling St George for 115 at Hurstville Oval thanks to Tony Clark's haul of 6-20.
Bankstown are 9-264 in thirds and 8-194 in fourths.
Play on day two resumes at 10.30am on Saturday.