Hibs knocked County out of the Scottish Cup with a 1-0 win at the end of November and they followed it up with another solid defensive display.
They completed the double with a 2-0 Scottish Premiership victory.
County were first to threaten in the fifth minute when a Graham Carey cross was only partially cleared but when the ball fell for Melvin De Leeuw he fired his shot just wide of the upright.
It was mostly County in the early stages but from their first corner of the match Hibs took the lead. Paul Cairney sent the ball over and Nelson rose above the County defence to head home.
The goal gave Hibs a real boost and they surged forward at every opportunity.
They came close again when Liam Craig tested County keeper Michael Fraser, the keeper could only parry the shot but when Ryan McGivern followed up he was ruled offside.
Hibs won a free-kick just inside the County half on the half hour mark but the ball took one bounce on its way through to Fraser.
At the other end County came close to a leveller when Carey swept in a 25-yard free-kick but the ball brushed the side netting on its way past.
The home side continued to push forward and a diagonal ball from De Leeuw landed at the feet of Kevin Luckassen who had the chance to drive into the box but the forward's first touch let him down and the chance was lost.
Both sides made a mess of free-kicks right at the end of the first half. Cairney swept one past Fraser's right hand post while Richard Brittain slipped before he ballooned his shot over.
County made a change at the start of the second half with Gary Glen coming on for Luckassen.
The home side made a lively start to the half and Brittain took advantage of a Rocco Quinn pass but failed to control the ball in the box.
Carey was still making a nuisance of himself on the left and his penetrating cross into the box in the 50th minute just evaded the Quinn.
Carey was the main outlet again a couple of minutes later when he cut inside and let fly with a right foot shot that clipped the outside of Williams' right hand post.
But it was the visitors who doubled their lead in the 55th minute when Forster stooped inside the six yard box to head in a Cairney corner.
County made a double substitution in the 67th minute with Orhan Mustafi and Alex Cooper coming on for De Leeuw and Ben Gordon.
The home side threatened again four minutes later when shots from Brittain and Quinn were both blocked in the box.
Carey came the closest yet for County with a free-kick in the 73rd minute which rebounded off the crossbar.
But it just was not County's day as Hibs held out for all three points.