The German beat Kelvin Wilson and Fraser Forster to a long ball to head into the net as the hosts stunned Celtic and consolidated their status as the Scottish Premier League's form team of 2013.
The win looked highly unlikely on 21 minutes after Charlie Mulgrew had scored direct from a corner and Gary Hooper chipped home as goalkeeper Michael Fraser endured a nightmare six minutes.
But County also scored twice in six minutes. A stunning volley from Grant Munro and Sam Morrow's close-range finish got them level before the break.
St Mirren and Dundee United had to settle for a share of the spoils after a 0-0 Premier League draw in Paisley, in which John Rankin was sent off for the visitors two minutes from time for a foul on McGinn just outside the box.
Dundee were left frustrated as Inverness struck late on through Billy McKay for a share of the spoils in a hard-fought 1-1 draw at Dens Park.
The home side's new interim manager John Brown was all set to celebrate his second win at the helm in the space of just a few days thanks to John Baird's excellent first-half opener but Caley Thistle hit back through McKay's 82nd-minute header.
Aberdeen were held to a 0-0 draw for the sixth time at Pittodrie this season as Motherwell became the latest team to frustrate the Dons.
Second-half goals from Murray Davidson and Gregory Tade sealed a 2-0 win over Kilmarnock and boosted St Johnstone's top-six aspirations.
In front of just 2,425 fans, McDiarmid Park's lowest weekend crowd of the season, the Perth side completed a hat-trick of victories this term over Killie.
The Ayrshire side rarely showed any threat going forward and their hopes of snatching a share of the spoils relied on Saints frittering away chances.