A polished display saw North End totally dominate their Lancashire rivals and step up their bid for automatic promotion.
Oldham caretaker boss Dean Holden, in charge for the first time after Lee Johnson’s move to Barnsley, found his squad decimated by injuries.
And Preston scored within the first two minutes as Paul Gallagher’s right-wing corner was powerfully headed home from eight yards by Paul Huntington.
North End’s Chris Humphrey hit the crossbar from long range before the visitors doubled their lead after 32 minutes as ex-Oldham loanee Daniel Johnson burst into the box and rifled in a 14-yard shot.
After Oldham had penalty appeals ignored, Preston struck again in the 52nd minute when Callum Robinson crossed from the left and the unmarked Joe Garner bundled in from close range.
Substitute Jermaine Beckford bagged the final goal eight minutes from time, turning home a pass from Sylvan Ebanks-Blake after a mistake by Oldham keeper Jake Kean.
Preston have not conceded a goal during their winning run, but Oldham have now suffered three consecutive losses.