Celtic trail table-toppers Rangers by three points and have played a game more than their Glasgow rivals, who they meet next Saturday lunchtime.
The match was switched to Livingston's Almondvale due to the poor playing surface at Fir Park, where Gretna have been tenants this season.
However, a poor crowd of 3,561 will not have done much to alleviate the ailing club's financial problems.
With Gretna scrapping for every ball, Celtic found it difficult to establish any rhythm in the early stages.
The visitors took 20 minutes to pose their first serious threat but defender Danny Hall was well positioned on the goal-line to nod away Scott Brown's clumsy close-range effort.
McGeady then cut in from the left flank and let fly from 20 yards only to see Greg Fleming claw his strike away from the top corner.
Shunsuke Nakamura's free-kick was easily gathered by Fleming but the keeper needed to look livelier to beat away a stinging long-range drive from Barry Robson.
Frustration got the better of Brown when his miscontrol led to him lunging at Ryan Baldacchino and the resultant yellow card earns him a three-game ban, although he will be available for the forthcoming Old Firm clash.
Gretna's stubborn resistance was broken three minutes before the interval and in the most straightforward of fashions.
A long punt from goalkeeper Artur Boruc reached Vennegoor of Hesselink on the edge of the penalty area and his header was volleyed home by McDonald from six yards.
Vennegoor of Hesselink should have extended the advantage a few moments later but he skewed a header wide from Nakamura's floated free-kick.
With 58 minutes gone, Nicky Deverdics squandered a great chance for Gretna when he scuffed wide from six yards after running on to Brendan McGill's low cross.
Celtic responded with their best passing move of the game, which culminated with McDonald's powerful strike being well saved by Fleming.
With 20 minutes remaining, Vennegoor of Hesselink got the goal that his industry merited.
The Dutch international striker popped up at the far post to head McGeady's deep cross past Fleming.
Gretna ran out of steam towards the end and Celtic added to their tally when substitute Samaras smartly stroked home McGeady's whipped delivery.
Vennegoor of Hesselink was denied a second goal when Fleming did well to block his strong downward header.
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