Gannon, who claimed eight wickets and scored 52 runs in last summer's season decider, took 5-57 at the WACA on Thursday to set up a 98-run first-innings lead.
Queensland were dismissed for 367 and WA were 3-106, a lead of 204 at stumps on day three.
Mitchell Marsh (40) and Hilton Cartwright (19) steadied the hosts' innings with an unbroken fourth-wicket stand of 59 and will look for quick runs before a final day declaration.
STUMPS, DAY THREE — WACA (@WACA_Cricket) #SheffieldShield 🟡⚫Mitch (40) and Hilts (19) guide us to 3-106 at the close of play, 204 runs ahead of Queensland 👊 Will we get a result tomorrow? Follow live: https://t.co/oexcYyugqB? pic.twitter.com/oUaW2jtg2HOctober 10, 2024
The fast bowlers from both sides toiled well on a pitch offering them little, with no batters dominating.
Jack Clayton (85) and Ben McDermott (62) extended their overnight fourth-wicket stand to 102 before Gannon had Clayton well caught down the legside by wicketkeeper Josh Inglis, after striking 12 fours.
The game tilted toward WA in the middle session when the Bulls lost 6-66 after being quite well placed at 4-301 in reply to 465.
In the space of 15 balls Queensland lost 3-2, with medium pacer Cartwright, who didn't take a Shield wicket last season, whipping out McDermott and Jimmy Peirson.
Between those two successful overs former Victoria paceman Brody Couch claimed his first Shield wicket as a WA player.
Gannon, who claimed the only wicket of the first session, took the last two wickets of a Queensland innings boosted by a late flurry from Mark Steketee (32).
His dismissal of Steketee gave the 35-year-old Gannon the sixth five-wicket haul of a first-class career which started with Queensland 14 years ago.
WA's Test opener Cameron Bancroft suffered a first-over pair, again caught behind off Michael Neser, lasting just four balls across the two innings.
Sam Whiteman and Jayden Goodwin added 47 before each fell to catches in successive overs, with the latter giving Australian U19 World Cup winner and paceman Tom Straker his first Shield wicket.
Marsh and Cartwright accumulated steadily against a probing attack and stymied the Bulls' hopes of blasting through the middle order, batting out the last 21.4 overs.
