The 22-year-old Dane's excellent form that saw him finish ninth in last week's Open Championship - his sixth top-10 finish of the season - continued as he moved onto 12 under par after completing his second round.
Starting one behind Spaniard Pablo Larrazabal, Olesen's first task of the day was to complete the four remaining holes of his first round caused by an earlier rain delay.
He picked up a birdie at the 17th to complete a first round 64 then after a quick turnaround enjoyed perfect conditions to sign for a second round 68.
Thomas Levet finished with a second round 70 to sit in second place three shots behind the Dane.
England's Richard Bland (67) was next best on eight under, with Dutchman Wil Besseling (72) on seven under par, together with home favourite Bernd Wiesberger, the Ballantine's Championship winner, who shot a superb round of 66 to move into contention.
Overnight leader Larrazabal struggled to maintain his momentum, and the Spaniard was on two over par after nine holes when play was suspended at Diamond Country Club in Atzenbrugg, with most players still on the front nine.
Olesen holed birdie putts from 12 and 25 feet at the fourth and fifth respectively, before striking his approach shot to three feet at the eighth hole.
"There was quite a strong wind out there at times," he told www.europeantour.com. "I struggled a bit round the turn and hit a few bad drives, but I managed to hit some good shots coming home, so I'm happy to get in on 12 under par. It's been a long day, but a very good one."