It was manager Colin Hendry's third win on the trot - his side's best run of the season - but at times the quality of the football served up by both sides was dour and error-ridden.
Blackpool started superbly with Keigan Parker bringing a magnificent save from Oldham keeper Les Pogliacomi in the ninth minute.
But from then on in difficult conditions on an uneven pitch both sides seemed to settle for mediocrity.
Oldham's commitment in midfield was marginally higher than Blackpool's, but they had little to show upfront.
Five minutes before the break they finally got behind a Blackpool defence which had been well marshalled by Rob Edwards, but on-loan Manchester United striker Kenny Cooper could only head weakly into the arms of Brad Jones.
Just after the break Hendry removed both his strikers, Simon Lynch and Zarko Grabovac, and replaced them with midfielders.
The tactic worked with veteran Paul Warhurst at last able to stamp some authority on Blackpool's midfield play with his ability to do the simple things well and keep the ball on the ground.
In the 71st minute Warhurst was involved in the build-up which won a corner. Edwards' outswinger was headed back into the box by Keith Southern and centre-back Clarke was there to ram home a shot from 12 yards out.
The goal seemed to take all the pressure off Blackpool who started to express themselves and with four minutes to go another fine piece of build-up saw Parker fire in a low cross which substitute Paul Edwards squeezed home at the near post.
Oldham did react and substitute Scott Vernon brought two late saves from Jones, but the Seasiders had done enough.