Barnsley turned on the style as they secured their first home victory in Sky Bet League One this term.
Gillingham were second-best throughout as the Reds netted twice in each half to make it seven points from their last three league fixtures.
The Reds had been two to the good at the interval thanks to Conor Hourihane’s piledriver and a fine dowward header from Sam Winnall.
In the second period the hosts upped the tempo in fine style.
Supersub Devante Cole - in front of his proud dad Andy - made it 3-0 when he slid in with pace and purpose to volley home Joe Dudgeon’s cross from close range.
The Gills reduced the arrears when Danny Kedwell netted in the 72nd minute.
He saw an initial spot-kick saved by Adam Davies after Dudgeon had upended Jermaine McGlashan in the box, but reacted first to tap home the rebound.
However, the Reds were rampant by this time and they bagged their fourth goal after 76 minutes.
This time a second substutute - Dale Jennings - guided an angled shot past Stephen Bywater after Hourihane had seen his free-kick blocked by the Gillingham wall.
There was even time for sub Kane Hemmings to see a shot strike the base of a Gillingham post as the Reds completed a thoroughly-deserved victory in front of an appreciate crowd of more than 9,00Barnsley (4-4-2): Davies; Brown, Nyatanga, Cranie, Dudgeon; Berry, Hourihane, Abbott, Treacy; Winnall, Lita.Subs: Hemmings, Jennings, Digby, M’voto, Bree, cole, Turnbull.
Gillingham (3-5-2): Bywater; Legge, Egan, Hause; A Morris, Hessenthaler, McGlashan, Dack, Hoyter; Kedwell, Dickenson.
Subs: G Morris, Fish, McDonald, German, Pritchard, Norris, Davies.