Morton put their league woes to one side as they moved into the semi-finals of this competition for the fourth year in a row with an impressive display.

Davie Irons, the Morton manager, admitted he was at a loss as to explain his side's league form after Brian Wake and Ryan McGuffie claimed victory in a dominant display. "I don't know how we can't do this in the league, its frustrating, but I don't want us to be known as a cup team," said Irons.

Gordon Chisholm, the Queens manager, who saw his side lose at home for the first time since last December, said: "There was just nothing about us, no sharpness, and it was just too much of an ask to play three games in eight days. I just couldn't see us scoring."

Queens showed early intent and on 10 minutes Stephen Dobbie sent a 20-yard dipping volley over before defender Craig Barr timed his run to get his head on a Jamie McQuilken corner from the right, which he just failed to keep on target two minutes later.

Dobbie threatened again on 17 minutes when his curling free-kick was pushed wide by Kevin Cuthbert, the Morton goalkeeper, before being scrambled clear.

Morton's previous three cup victories came away from home, scoring 13 goals and they may have added to that tally three minutes from the break when Stevie Masterton curled in an angled 25 yard free-kick, which Cammy Bell, the Queens goalkeeper, did well to turn over the bar.

Morton made the breakthrough in 48 minutes when Wake ran in from the left to drill McGuffie's pass low past Bell from 15 yards.

Irons' side booked a last four place in 77 minutes when McGuffie curled a 20-yard shot high past Bell from the left-hand side of the area.