Charlie McCann scored the only goal of the game as Forest Green made it back-to-back victories in the National League.
Rovers pushed for more in the second half but Oldham goalkeeper Matthew Hudson kept the scoreline at one.
Manager Steve Cotterill named one change the side Easter Monday side who beat Tamworth with Jamie Searle replacing Ted Cann in goal with the West Brom loanee ruled out with a thigh injury.
Joe Quigley went close in the opening exchanges heading a corner goal bound but Hudson was able to save.
Rovers took the lead on the cusp of half-time when Quigley's tenacity and hold-up play found midfielder McCann who cut inside and fired into the bottom corner.
McCann almost doubled his tally soon after the break but his drilled effort from the edge of area bounced wide.
Hudson had to be in fine form again - this time to deny Kyle McAllister and Jordon Garrick on the follow-up.
Rovers dug in late on for another three points to add to the tally as we approach the playoffs.
FGR: Searle, Long, Inniss, Harries (Bunker 28), Robson, May, McCann, Sercombe (Jenks 90), McAllister (Osadebe 88), Garrick (Knowles 71), Quigley (Cardwell 82).
Subs not used: Doidge, Fleming.
Oldham Athletic: Hudson, Sutton (Ogle 64), Raglan, Hobson, Kitching, Conlon (Harratt 63), Pett, Hammond (Pritchard 50), Yoganathan (Evans 76), Uchegbulam, Fondop (Garner 55).
Subs not used: Donaghy, Rossiter.