Maher has been in red-hot form aboard 11-year-old grey mare Cella in Denmark helping Britain top the leader board after the speed class and the first round of the team competition.
And the 30-year-old, part of Britain's Olympic gold medal winning team at London 2012 last summer, produced another brilliant clear opening up for the quartet in Herning.
Michael Whitaker and Viking were unlucky to earn five faults however William Funnell and Billy Congo put in a well-deserved clear round with Scott Brash last up for Britain.
Brash, like Maher and part of the Olympic gold medal winning team from London 2012, was the final competitor to go with Britain leading with only one fence in hand.
A solitary rail fell early on in the course but Brash held his nerve aboard Olympic ride Hello Sanctos as Britain claimed gold ahead of runners-up Germany, who were just behind with 12.77 points. Sweden claimed bronze.
Only Germany some 17 years ago have won Olympic and then European gold while Maher leads the individual competition going into the final on Saturday with zero penalties.
"She [Cella] has been unbelievable, I honestly felt it was the best she's jumped in the three days. The bigger the jumps, the harder she tried," said Maher.
"She'll get a nice day off and I'm looking forward to going into the Individual Final on Saturday with a zero score. She's a once in a lifetime horse and here in Denmark she feels better than ever."