C Palace 0 Bristol City 1
Ipswich 2 Cardiff 0
Peterborough 1 Sheff Utd 0
Preston 1 Doncaster 1
QPR 2 Plymouth 0
Watford 0 Swansea 1
West Brom 1 Sheff Weds 0
The Baggies, who moved above Nottingham Forest on goal difference, missed chances through Chris Brunt, James Morrison, Graham Dorrans, Youssouf Mulumbu and Luke Moore in the first half.
And the pattern continued as Moore's effort was blocked by Darren Purse and keeper Lee Grant kept out Jonas Olsson, Ishmael Miller, Morrison and Dorrans before Koren finally found a way through from long range.
Fourth-placed Swansea found the perfect response to Saturday's last-gasp defeat at Forest, their first reverse in 13 games, as they beat Watford 1-0 at Vicarage Road.
Finland striker Shefki Kuqi was on target for his third goal in nine appearances for the club, heading home Craig Beattie's cross from close range, and Heidar Helguson headed against the bar and was twice denied by Swans keeper Dorus De Vries as the Hornets failed to find an equaliser.
Ipswich's impressive home record continued as on-loan Sunderland striker Daryl Murphy scored twice - his first goals in five games - to earn them a 2-0 win over Cardiff.
Roy Keane's side, who moved four points clear of the relegation zone, are now unbeaten in 12 matches at Portman Road.
Craig Mackail-Smith's landmark goal earned Peterborough a 1-0 victory over Sheffield United at London Road.
All five of Posh's wins this season had come at home and they made that six courtesy of Mackail-Smith's 100th senior goal and his first since mid-December.
Tommy Rowe could have made it two but shot over after keeper Mark Bunn's poor punch, while the Blades' best chance came in injury time when Gabriel Zakuani blocked Mark Yeates' shot and, from the resulting corner, Nick Montgomery shot wide.
Billy Sharp missed a second-half penalty as Doncaster drew 1-1 with Preston at Deepdale.
James Hayter, on his 100th appearance for Rovers, fired a shot into the bottom corner from 18 yards for his sixth goal of the season in the 29th minute before Neil Mellor levelled three minutes prior to the break from close range.
Sharp's spot-kick was saved by Andy Lonergan in the 56th minute, leaving Sean O'Driscoll to wait for the 200th win of his managerial career.
Neil Warnock's fine start to life at QPR continued after a penalty by Adel Taarabt - after Kari Arnason had fouled Tamas Priskin - set them on the way to a 2-0 victory over second-from-bottom Plymouth.
Damion Stewart headed the second from Taarabt's free-kick and Alejandro Faurlin turned another set-piece from the midfielder wide and was later brilliantly denied by keeper David Stockdale
In the night's other game, Chris Iwelumo scored 17 minutes from time to earn Bristol City a 1-0 win at Crystal Palace - though the on-loan Wolves striker then left the field injured with five minutes remaining.