MK Dons won their third straight home fixture in League One to climb to third in the table, as new Southampton manager Nigel Adkins tasted defeat in his first game in charge of Saints.
Dons boss Karl Robinson turned 30 on Monday and enjoyed a belated birthday present as his team bounced back from their defeat at Brighton on Saturday.
Angelo Balanta struck the opening goal with a precise right-foot finish after 72 minutes, while Peter Leven secured the points close to the final whistle after Kelvin Davis parried his initial effort.
It was Southampton's fourth straight defeat without scoring a goal since the sacking of Alan Pardew.
The home team were compact in midfield, organised in defence and made good use of the width of the pitch at stadium:mk, but for large periods of the first half it was Southampton who looked most likely to open the scoring.
Adkins, who was given a generous reception by the Saints fans after taking his place in the dug-out, saw his team create several good chances.
Rickie Lambert forced a sensational fingertip save from David Martin with an opportunistic dipping strike, while the impressive Morgan Schneiderlin shot narrowly over with a technically brilliant volley from just outside the area.
Schneiderlin had a later effort palmed clear by Martin, while Alex Oxlade-Chamberlin, who looked dangerous when running at goal, drilled the follow-up wide.
MK Dons struggled to retain possession and spent periods chasing the game but they did create two good first-half chances.
Davis made a brilliant reaction save to deny Lewis Guy, who deftly controlled a square ball from Luke Chadwick before shooting from 12 yards.
Adkins left Scunthorpe to take over at Southampton at the weekend
Central defender Mathias Kouo-Doumbe then wasted a great chance minutes before the break, heading over a Leven free-kick despite being just eight yards from goal.
Another precise delivery from Leven shortly after the restart found Jabo Ibehre, on as a first-half substitute after Sam Baldock picked up an injury, but the replacement also headed over.
Leven tried to catch Davis off his line with an audacious 60-yard effort that the keeper comfortably caught, while Balanta, on as a 55th-minute replacement for Dietmar Hamann, narrowly missed after a surging run down the left.
The home team had improved after the restart and might have been awarded a penalty after Jermaine Easter went down after tangling with Daniel Seaborne but referee Fred Graham waved play on.
But there was no debate about Balanta's goal, which came at the end of a well-constructed build-up that started when Luke Chadwick picked out skipper Dean Lewington with a superb raking pass.
Lewington then played a cracking through ball, with the outside of his right boot, that Balanta controlled before guiding his strike beyond Davis.
Easter almost secured the points with a header that rebounded off the crossbar, but Leven made the points safe with his close-range finish.
MK Dons boss Karl Robinson told BBC Three Counties Radio:
"We knew we'd have to weather a storm, with a new manager and a new style of football.
"We knew that if we got over the first 10-15 minutes that our quality would tell. We thought we'd sit off them, let them have a bit of play and hit them on the counter.
"Tonight, luckily, it's worked in our favour, or tactics worked."
Live text and stats
Wednesday, 15 September 2010
Npower League One
06 O'Hanlon (Wilbraham 82)
16 Hamann (Balanta 55)
26 Chadwick yellow card
10 Baldock (Ibehre 11)
04 Schneiderlin yellow card
26 Chamberlain (Holmes 90+1)
22 Connolly (Wotton 65)
Ref: GrahamAtt: 8,133
Attempts on target
Attempts off target
93:36 The ref blows the whistle to begin the match.
90:00+0:38 Substitution Alec Chamberlain goes off and Lee Holmes comes on.
90:00 The referee signals the end of the game.
86:57 Assist on the goal came from Dean Lewington.
86:57 GOAL - Peter Leven:MK Dons 2 - 0 Southampton A goal is scored by Peter Leven from inside the six-yard box to the top left corner of the goal. Milton Keynes Dons 2-0 Southampton.
84:11 Inswinging corner taken left-footed by Peter Leven from the right by-line, Richard Lambert manages to make a clearance.
81:27 Kelvin Davis takes the free kick.
81:27 Substitution Aaron Wilbraham is brought on as a substitute for Sean O'Hanlon.
81:27 Foul by Peter Leven on Morgan Schneiderlin, free kick awarded.
80:23 Outswinging corner taken by Jason Puncheon from the left by-line.
79:02 Jermaine Easter is caught offside. Kelvin Davis restarts play with the free kick.
76:04 Outswinging corner taken from the left by-line by Peter Leven, clearance made by Morgan Schneiderlin.
71:05 Jermaine Easter provided the assist for the goal.
71:05 GOAL - Angelo Balanta:MK Dons 1 - 0 Southampton Angelo Balanta grabs a goal from the edge of the penalty box to the bottom right corner of the goal. Milton Keynes Dons 1-0
64:41 The assistant referee signals for offside against Jabo Ibehre. Indirect free kick taken by Danny Butterfield.
64:04 Substitution Paul Wotton on for David Connolly.
63:34 Short corner taken by Jason Puncheon from the right by-line.
61:54 Angelo Balanta fouled by Danny Butterfield, the ref awards a free kick. Dean Lewington takes the direct free kick.
59:35 Outswinging corner taken by Jason Puncheon from the left by-line played to the near post, clearance by Luke Chadwick.
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