Motherwell beat Dundee United 2-1 on Friday night to become the first team to book their place in Sunday's draw for the Premier Sports Cup semi-finals.
Zach Robinson fired the Steelmen in front with a superb shot in first-half injury time but Luis Moult equalised with a spectacular strike after 83 minutes.
Stuart Kettlewell's men won the match in added time when Lennon Miller converted from the penalty spot to seal a last-four place on November 2/3.