The Third Division outfit - currently top of the table - had a fully fit squad as they sought to follow up their giant-killing exploits after victories over St Mirren and Queen of the South.
But Rangers chief Walter Smith used the opportunity to field an experimental side, resting a number of key players, including skipper Barry Ferguson.
Roy Carroll replaced Allan McGregor in goal, while Kirk Broadfoot, Amdy Faye, Ugo Ehiogu, Chris Burke, Novo, and Alan Gow all featured, with fit-again Belgian Buffel having to settle for a place on the bench.
There was an obvious gulf in class between the teams and the Methil side struggled to create any clear-cut opportunities.
And it was no surprise when Fifers goalkeeper Willie McCulloch could do nothing to stop an impudent strike by Spaniard Novo as the fringe Light Blues forward drove home from distance with the ball sailing into the roof of the net.
But, moments later, East Fife, who had moved the tie to Dunfermline's East End Park to accommodate Rangers' travelling support, had a decent chance of their own.
Ryan Blackadder, who had replaced Gary Greenhill in the starting line-up, had a go from distance, only for his effort to crash off the crossbar and over.
However, with Rangers predictably in control, the SPL leaders grabbed a second, the prolific Boyd tapping in from close range after East Fife failed to clear a testing corner from the impressive Burke.
The visitors kept a tight grip on proceedings in the second half and former Osasuna defender Cuellar got on the scoresheet, using his aerial power to add a third.
Buffel returned after his long injury absence for Rangers and he immediately won a spot kick, the midfielder brought down by McDonald. Boyd calmly converted.
Dave Baikies' side's best chance to make an impact came from an inswinging corner by Douglas Cameron, but the danger was averted with a clearance by Charlie Adam in the 73rd minute.
However, Carroll was rarely troubled and the Glasgow side completed a professional job as they seek to win this season's first piece of silverware on offer.
East Fife: McCulloch, McDonald, Fotheringham, Smart, Tweed, Blackadder (O'Reilly 63), Gordon (Walker 62), Stewart, McManus (Nicholas 81), Young, Cameron. Subs Not Used: Fox, Martin.
Rangers: Carroll, Whittaker, Broadfoot, Faye, Cuellar, Ehiogu, Burke, Adam (Emslie 80), Boyd (Cousin 72), Novo (Buffel 60), Gow. Subs Not Used: Graeme Smith, Papac.
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