Fabian Yantorno set up two goalsand scored the other
Gretna had to come from behind to dump Second Division Cowdenbeath out of the CIS Cup and record their first win at Fir Park - in front of just 342 fans.
The SPL side went behind after 14 minutes at their temporary home when former Gretna midfielder John O'Neil sent a 24-yard drive in off the bar.
Craig Barr flicked in a Fabian Yantorno free-kick to level after 52 minutes.
Yantorno flicked over goalkeeper David Hay to head home after 85 minutes and Allan Jenkins drove home the third.
Gretna had rested Aurelien Collin and Paul Murray, while new French striker Mikael Buscher did not receive international clearance in time and had to sit it out.
And there was an element of needle to the tie with former Gretna players Mick Galloway, Bryan Gilfillan and O'Neil on the pitch and Danny Lennon in the dugout. Gretna went close early on when midfielder Erik Paartalu cracked a rising volley over the bar from the right angle of the box.
But they went behind as O'Neil received the ball 25 yards from goal and cracked a fantastic shot into the net off the underside of the bar.
Just a minute later, Gretna almost levelled when McMenamin went around Hay, but John Armstrong raced back to block on the line.
Battling Cowdenbeath were content to get players behind the ball and dig in as the game became scrappy with Gretna lacking the creative spark to unlock their defence.
And, with the small number of fans smattered around the ground, there was little in the way of atmosphere to help the players lift their game.
Gretna came out with more purpose after a half-time blast from manager Davie Irons.
And, in the best move of the match, Nicky Deverdics turned his marker and played in Jenkins, who laid the ball back for David Graham to cross for McMenamin to power in a header that shaved the bar.
One minute later, Yantorno bent in a superb free-kick that Barr flicked on to score.
It was the Yantorno show after that and he was unlucky on the hour when he curled in a brilliant shot to beat Hay, but the ball came back off the crossbar.
Yantorno then beat three men with his ball-juggling skills and was fouled by Gilfillan before picking himself up and firing in the free-kick that had Hay stretching to turn over.
But he was not to be denied and the late double left Gretna breathing a sigh of relief.
Gretna: Fleming, Barr, Cowan, Grainger (Collin 45), Skelton, Paartalu (Deverdics 45), Osman, Jenkins, Graham (McLaren 79), McMenamin, Yantorno.
Subs Not Used: Mathieson, Hogg.
Goals: Barr 52, Yantorno 85, Jenkins 88.
Cowdenbeath: Hay, Baxter, John Armstrong, David Armstrong, Adamson, Patrick Scullion, Gilfillan, O'Neil (Howatt 26), Galloway, Desley (Hill 70), Dalziel (McConalogue 79).
Subs Not Used: Allison, Ondrige Matusik.
Booked: Baxter, Gilfillan.
Goals: O'Neil 13.
Att: 342
Ref: B Winter
