Gretna, slightly against the run of play, went ahead in the 11th minute. Debutant Allan Jenkins sent Gavin Skelton dashing down the left flank after Stewart Greacen had lost possession near the centre circle. Kenny Deuchar rose to the far post cross and his downward header crept in, although Stefan Gonet appeared to have the ball covered.
Jim McAlistair lead the riposte, but his shot from 18 yards was straight at Alan Main. Gretna were knitting together impressively while Morton could not keep sufficient possession to mount significant attacks.
Chris Innes put the league leaders further ahead just after the half hour, firing a rising shot from the angle of the box after John O Neil's cross found him in splendid isolation.
Gonet saved David Nicholls' drive before Derek Lilley glanced in an Andy McLaren cross to reduce the arrears. Gonet then threw himself desperately to block Deuchar's point-blank header.
Ton pushed Peter Weatherson up front and the home side dominated after the break. McLaren, Kevin Finlayson and Chris Millar all went close before Gonet had to be alert to foil O'Neil.
Cappielow Park went berserk when Morton equalised 11 minutes from time with a scintillating goal. David McGregor cleared a Gretna corner and passed to McLaren, whose deft flick sent Jason Walker sprinting off down the right wing.
Walker's deep cross was met by Millar at the far post, and Weatherson bundled the ball in from a couple of yards.