Barnsley boss Danny Wilson made two changes to his side for the trip to MK Dons.
Manchester United loan midfielder Ben Pearson returned to the starting line-up having missed last Saturday’s clash with Doncaster Rovers because of an ankle injury.
Young defender Mason Holgate missed out through suspension, the first of three games out after his red card against Rovers last weekend.
Holgate’s omission handed new signing George Williams the chance in defence, while Dale Jennings didn’t even make the match day squad.
The Reds were also without the injured Martin Cranie, James Bree and Sam Winnall.
A mistake from Williams allowed Daniel Powell to unleash a right-foot shot on target, but keeper Ross Turnbull saves well.
MK Dons thought they had taken the lead in the 33rd minute but William Grigg’s effort was ruled out for offside. Turnbull made a fine save to tip Dele Ali’s original shot against a post, before Grigg netted only to find mself ahead of play.
Baker found space but lashed a powerful shot just wide of the target as Dons looked to score before the break.
Stoke City loan striker George Waring headed on to the roof of the MK Dons’ net from Conor Hourihane’s delivery.
Turnbull parried a close-range shot from Baker and the Reds avert the danger.
Manchester United loan midfielder Ben Pearson blazed over with left-foot effort for Barnsley.
Deli Alli put the Reds behind in the 57th minute.The midfielder, unmarked on the edge of the box, cut inside and beat Turnbull with a sweet left-foot strike into the bottom left corner for his 12th goal of the season.
A minute later Grigg nearly made it 2-0 l as he just failed to turn in Baker’s shot across the face of the box.
Wilson’s men were 2-0 down in the 63rd minuute when bad defending from the Reds saws Grigg bag the second goal the hosts were craving. The former Brentford striker calmly rounded Turnbull and slotted into an empty net.
Man of the match Grigg somehow missed from six yards out as the Dons sought a third goal.
Devante Cole shot straight at Turnbull as the Reds slumped to a fifth successive league away defeat. They last won away in the league on November 1 when then they beat Sheffield United 1-0 at Bramall Lane.
MK Dons: Martin, Spence, McFadzean, Kay, Lewington (c), Potter, Alli,Baker, Bowditch, Powell, Grigg. Subs: McLoughlin, Hodson, Baldock, Green, Carruthers, Cole, Clarke-Harris.
Barnsley: Turnbull, Berry, Nyatanga, Hourihane (c), M’voto, Smith, Williams, Pearson, Lalkovic, Waring, Kiwomya. Subs: Davies, Ramage, Scowen, Digby, Oates, Phenix, Lita.
Referee: Christopher Kavanagh