MK Dons moved back into the automatic promotion places courtesy of a 1-0 win at Colchester United.
Kyle McFadzean and Will Grigg returned to the starting XI, the former after serving his two-game suspension, while George Williams came straight in after rejoining the Club on loan from Fulham.
The hosts were the first to threaten as early as the opening 60 seconds when Gavin Massey saw a 20-yard effort deflect wide – the referee spotted an infringement in the Dons’ favour from the resulting corner.
Ian McLoughlin, continuing in goal with David Martin out injured, saved Chris Porter’s 25-yard drive on six minutes, following some good pressure from Karl Robinson’s men at the other end.
As the clock ticked towards the 15-minute mark, the Dons were enjoying the majority of the possession as they looked to manoeuvre their opponents and create chances.
But it was from a set-piece that they almost went ahead when Jordan Spence forced Sam Walker into a fine finger-tip save after forcefully meeting Carl Baker’s free-kick from the right on 21 minutes.
Alli dragged a speculative effort past the post five minutes later, prior to Dean Lewington heading a McFadzean cross wide of the target after the Dons had recycled a corner.
Darren Potter pulled a drive the wrong side of upright and the hosts had to be alert to clear two dangerous crosses into their box as the men from MK1 upped the ante as the game approached half-time.
A good break down the left, involving Lewington and Grigg, presented a chance for Baker on 42 minutes but, after twisting and turning, his shot was well blocked.
The Dons’ pressure finally told on 44 minutes when Baker’s corner was only cleared as far as Kay, who lifted the ball back over the top and Alli confidently swept home past Walker from 12 yards – his 14th goal of an already-memorable campaign for the 18-year-old. 0-1
Robinson’s men started the second half in confident manner, keeping their opponents at bay whilst also trying to increase their lead at the other end.
However, McLoughlin had to be at his very best to deny the hosts from levelling on 59 minutes, flying across to his right to palm away Massey’s fierce volley from 18 yards.
After more good work by Williams, Daniel Powell turned his man and stung the palms of Walker with a powerful 20-yard drive as the Dons posed a threat going forward.
Williams, who had an impressive night, was replaced by Samir Carruthers with just over 15 minutes remaining before Devante Cole came on for Grigg five minutes later.
The Dons were in control of the contest but Kay had to be in the right place at the right time as the clock ticked into injury-time, clearing the danger from inside the six-yard box as the U’s looked for an equaliser.
In truth, Robinson’s men saw out the game very comfortably to earn an important victory.
MK Dons: McLoughlin; Spence, Kay, McFadzean, Lewington (c); Potter, Alli (Reeves 64); Powell, Baker, Williams (Carruthers 73); Grigg (Cole 80).
Unused subs: Burns, Hodson, Flanagan, Green.
Bookings: McFadzean, Potter.
Goals: Alli (44).
Attendance: 2,974 (248 Dons fans).