After surviving the halfway cut with nothing to spare at three over par, McGrane birdied three of the last four holes on the front nine then collected further birdies at the 11th and 15th.
Up to two under as a result the 39 year old from County Meath was up into a tie for 14th on the course where October's Ryder Cup will take place.
German Marcel Siem and Australian Andrew Dodt led overnight at six under by one from Dane Thomas Björn, with Europe Captain Colin Montgomerie four back and yet to tee off again.
McGrane posted a 66, one outside the course record, to be two under after 54 holes, but England's David Lynn was threatening to take the early clubhouse lead off him when he also turned in 33 and birdied the tenth and 11th.
At three under Lynn was up to joint ninth and was alongside Northern Irishman Graeme McDowell, who had a hat-trick of birdies from the second to boost his chances.