The innovative event saw 64 players qualify for the nine-hole stroke play knockout after 36 holes of stroke play and by Saturday night the 144-man field had been whittled down to eight.
Colsaerts had finished five shots off the lead but claimed wins over Richie Ramsay, Lorenzo Gagli and Joachim B Hansen in front of a vociferous home crowd on day three to set up a quarter-final against England’s James Heath.
In the other last-eight matches, Mike Lorenzo-Vera will face Benjamin Hebert in an all-French clash, another Frenchman in Victor Perez will take on Scotland’s David Drysdale, and Spaniards Jorge Campillo and Adrian Otaegui will go head-to-head.
There were four Belgians still involved at the start of the day but with tournament host Thomas Pieters, Thomas Detry and Christopher Mivis all falling in the last-64, the pressure was put on Colsaerts, not that it showed.
He moved one ahead after Dane Hansen could not get up and down on the second and led by two when he holed a 12-footer on the fourth. A brilliant three wood set up an eagle from ten feet on the seventh before Hansen claimed a consolation birdie on the last.
“I’m enjoying this a lot,” said Colsaerts. “It’s pretty cool when you play well in front of home crowds like this. A lot of people have turned up. You can feel the good vibe and when you pull it off, it’s actually quite a cool feeling.
“Everybody’s smiling, everybody’s having a good time. There was a couple of waves on 16 and 18 when I walked on to the green.”
Swede Robert Karlsson bogeyed the first and Heath made a double on the fourth before both men birdied the fifth.
A bogey from Karlsson on the ninth sent him up the play-off hole for the third match in a row and he went a long way left off the tee to make a mess of his 33rd hole of the day, allowing Heath to advance with a par.
I’m enjoying this a lot. Everybody’s smiling, everybody’s having a good time – Nicolas Colsaerts
Lorenzo-Vera was the first man through after a scrappy encounter against Englishman Matthew Baldwin.
Both men bogeyed the first and Baldwin then dropped a shot on the third and made a double on the fourth, with Lorenzo-Vera also dropping a shot. The 33 year old hit a stunner of an approach into the fifth to lead by three and the gap would stay that way with both men birdieing the short seventh.
Hebert had to survive an excellent fightback from Scot Stephen Gallacher to make his way through.
Gallacher went a long way right off the tee on the first and birdies from Hebert on the next two holes meant the gap was five shots. Gallacher made a hat-trick of gains from the sixth and a Hebert bogey on the seventh cut the gap to one but Gallacher bogeyed the last.
Otaegui beat England’s Matthew Southgate by one-shot in a high-class encounter.
The 25 year old got a fortunate bounce from the trees and made the most of it on the first but Southgate birdied the next two, hitting the flag on the third and having to hole a long putt. A stunning approach on the next saw Otaegui hit back before Southgate bogeyed the fifth.
A smart downhill putt from Otaegui on the seventh gave him a two-shot cushion but Southgate birdied the next to set up a tense finish.
Campillo and England’s Richard McEvoy both bogeyed the first and fourth and the top seed bogeyed the next before reeling off a hat-trick of birdies to get back to level par. McEvoy could only respond with a single gain on the eighth and Campillo won by one.
Josh Geary birdied the first and had a two-shot advantage when Drysdale bogeyed the third before a bogey on the fourth from the Kiwi cut the gap. A two-shot swing on the seventh put Drysdale ahead but Geary birdied the eighth to take it to extra holes.
A poor chip meant Geary could only make par on the second trip up the play-off hole and Drysdale advanced with a birdie.
Perez bogeyed the second and fifth to sit two behind but when he drove the seventh for a ten-foot eagle and Englishman Oliver Fisher made a bogey after a poor tee-shot, the match was turned on its head. Fisher then bogeyed the last and Perez won by two.