Colsaerts put together a bogey-free 8-under 62 in Thursday's first round but was inconsistent in finishing at even-par 70 in the second round for a 36-hole total of 8-under 132.
Shiv Kapur, who had three birdies and a bogey for a 2-under 68 Friday, pulled into a tie with Colsaerts. Todd Hamilton (67 Friday), Jean-Francois Lucquin (67) and Christian Nilsson (65) are tied for third at 7-under. Martin Kaymer (67) leads a pack of eight players tied for sixth at 6-under 134.
Colsaerts was 3-under under after his first 14 holes Friday but lost his drive in the heather at No. 15 and ended up with a double bogey 6. He birdied No. 7 but finished with consecutive bogeys at Nos. 8-9 and dropped into a tie for the lead.
Kapur's lone bogey came at the par-3 15th hole. He had birdies at Nos. 8, 12 and 17.
Kaymer was the only golfer among the leaders to complete Friday's round without a bogey.