Gillespie, dropped from the Australian team during the ill-fated Ashes campaign in England in August, bowled with the sort of movement and zip he showed in his prime as Victoria were dismissed for 149 in just over two sessions.
South Australia began disastrously and reached stumps at 58 for two, to trail by 91 runs with eight wickets in hand.
SA had further disappointment with news that captain Darren Lehmann ruptured a ligament in his right thumb in the field during the first session and is unlikely to play again this year.
A lower-order fightback highlighted by Chris Simpson's 62 allowed Queensland to struggle to 266 against Shield leaders NSW on the first day of their four-day game in Sydney.
NSW were six for one in reply at stumps after Phil Jaques fell to Andy Bichel's bowling in the final over for two.
Wicketkeeper Chris Hartley (37), Ashley Noffke (31) and veteran pace bowler Andy Bichel (39) added some backbone to the Queensland innings after the first five wickets fell for just 89 runs.
But Simpson held the innings together, scoring his fourth first-class half-century and hitting six fours and two sixes in his two-hour stint.