Nicky Law fired in the opener at Central Park to give Ally McCoist’s side an early boost and Kyle Miller scored an own goal after 55 minutes.
David Templeton then ensured the points were safe when he drilled home five minutes from time.
Midfielder Law claimed the opener with barely three minutes on the clock, the midfielder playing a one-two with Kris Boyd before powering into the home penalty area and slotting the ball into the far corner.
Cowdenbeath rallied though and went close through Kudus Oyenuga, the Dundee United loanee hitting a free-kick just over the crossbar before Sean Higgins went even closer to an equaliser.
The ball broke to Higgins on the edge of the box and his seemingly innocuous scuffed shot beat Steve Simonsen in the Rangers goal before hitting the foot of the post.
Cowdenbeath keeper Robbie Thomson kept out a low strike from Rangers captain Lee McCulloch just after the break but he was beaten soon afterwards.
Boyd’s cross appeared to be harmless enough but defender Miller’s attempted clearing header came back off the crossbar before crossing the line.
Miller attempted to atone for his mistake but his long-range free-kick was pushed round the post by Simonsen before drilling just wide with another sighter at goal.
McCoist’s side were still creating chances though and Lewis Milne had to clear substitute Jon Daly’s header off the line before Templeton pounced in the closing stages.
Ian Black took advantage of some gaps in the home defence and picked out Templeton, who slotted his shot inside the far post to seal the victory.