Ormsby, who is looking his first European Tour title, completed 36 holes at 7-under-par 135.
James Morrison posted a 2-under 69 and is alone in second place minus-6. Christian Nilsson also shot 69 Friday to move into third at 5-under 137.
First-round leader Fredrik Andersson Hed tripped to a 2-over 73 to dip into fourth place at minus-4 at Aa Saint Omer Golf Club.
Ormsby played the back nine first on Friday and opened with a pair of pars. He birdied the 12th, but gave that shot right back with his second bogey in two days on the par-4 13th.
The Australian birdied the 14th and 16th to move to 3 under. He cruised to seven straight pars around the turn.
Ormsby birdied six and seven, both for the second day in a row, to move to minus-5. He jumped into the lead thanks to a chip-in eagle on the par-5 ninth, his last.
'I stood on the ninth tee thinking about a birdie, so to chip in for eagle was a big bonus,' Ormsby stated. 'It was a great end to a very pleasing round. I haven't struck the ball that well for a very long time, particularly on the back nine.
'Earlier this week, my confidence started coming back, and all of a sudden the putts start dropping too. So instead of just chasing the cut line, you're starting to chase the leaders. Now I am the leader by one, which is obviously a great position to be in.'
Morrison also played the back nine first on Friday and collected a single birdie on the par-5 14th to go with eight pars on his opening nine.
The 24-year-old parred seven in a row from the 15th before stumbling to a bogey on the par-3 fourth. Morrison closed with birdies on seven and nine, both par-5s that he also birdied in the opening round.
'The only bogey I made was down in a plugged lie in the bunker,' explained Morrison. 'To have only one bogey after 36 holes round here must mean I'm playing pretty well. So I'm very happy.'
The cut line fell at 4-over 146 with 79 players moving on to the weekend.