The 19-year-old gave Latics the lead going into half time and Jonathan Forte doubled that just before the hour mark with a neat finish.
Turner doubled his tally for the night three minutes later and Latics held on to a second successive clean sheet to seal the double over Dale.
Latics started the game brightly and could have taken the lead in the opening minute of the game.
Carl Winchester received the ball on the right hand side and he cut past the last defender but Jamie Jones pulled off a great save, and he denied Turner on the rebound.
Rochdale started to grow into the game but it was Latics that were enjoying the better chances.
Mike Jones played a lovely reversed ball through to Jonathan Forte on 15 minutes and he crossed into the centre but Dale just managed to hack the ball clear.
Coleman, who was making his second professional start for Latics, was almost caught out a minute later but Jamie Allen could not profit from his mistake.
Jones, who is known for his goals outside the box, almost made it seven for the season on 18 minutes as he rifled a shot from 35 yards but his shot smashed the crossbar and out for a goal kick.
Coleman had to be aware a minute later as Peter Vincenti shot from 25 yards but he tipped the ball around the post.
That was the last piece of action for the Dale man as he limped off with an early injury.
Turner and Forte was causing problems for Rochdale's defence and the 19-year-old found a way past the defence, fed the ball to Winchester but he shot over the bar from just inside the box.
Latics managed to take the lead on the half hour mark through Turner.
It was great work on the left hand side from Mat Sadler who set up the goal. He received the ball from a throw-in, knocked it over the head of the defender, shot at goal and Turner was there to put home the rebound to score in his second successive home game.
The goal lifted the supporters but minutes later, there was a stoppage in play as both Sadler and Allen clashed heads forcing the Dale man to be substituted.
Dale's injury hit day took another twist as they were forced into their final change of the night as Oliver Lancashire replaced the injured Stephan Dawson.
Into additional time in the first half, Luke Woodland almost doubled Latics' lead with a ferocious effort from outside the box which looked a goal from the moment it left his boot but it just whistled past the post.
Rochdale shaded the early possession in the second half and went close through Michael Rose's shot from distance but Coleman watched it over the bar.
There was an altercation between Connor Brown and Ian Henderson ten minutes into the second half which seemed to lift the supporters and they were rewarded with a goal on 58 minutes.
Jones' cross found Forte whose first shot was blocked but he smashed home the rebound to double Latics' lead.
Two became three on the hour mark as Turner grabbed his second goal of the game.
The ball seemed to last an age at his feet inside the six yard box but he danced around several challenges and placed the ball beyond Jamie Jones to make it three for Athletic.
He was soon replaced and received a standing ovation from the home supporters for his night's work.
Dale started to grow back into the game but Michael Rose and Reuben Noble-Lazarus saw their shots saved by Coleman.
Woodland was proving to be an inspirational figure in the midfield as he broke up the play and set up attacks for Latics.
Rochdale's night worsened on 76 minutes as they were forced down to ten men as Ashley Eastham went off through injury.
Dale continued to press but Latics' defence were standing resolutely.
With five minutes of the game remaining, Woodland, who received the Optima Cars man of the match, left the field to the roar of the supporters for his impressive evening's work.
Latics saw the game out confidently and go into Saturday's game on the back of two straight victories.
Oldham Athletic: Coleman, Brown (Kusunga 73'), Gerrard, Lockwood, Sadler, Woodland (Dieng 85'), Winchester, Jones, Philliskirk, Turner (Poleon 64'), Forte.
Subs not used: Kean, Mellor, Bove, Jacobs.
Rochdale: Jones, Bennett, Eastham, Vincenti (Noble-Lazarus 19'), Dawson (Lancashire 43'), O'Connell, Allen (Hery 38'), Rose, Cannon, Kennedy, Henderson.
Subs not used: Lillis, Brandy, Tanser, Bunney.
Goals: Oldham Athletic (Turner 30', 61', Forte 58') 1-0 Rochdale
Attendance: 5,322 (1,319 visiting supporters)