A second half goal from Stefan Lavery saw Dungannon Swifts beat Donegal Celtic and book an Irish Cup semi-final date with Crusaders on 31 March.
The quarter-final replay began brightly as Robert Robinson pushed a JP Gallagher shot round the post early on.
Kieran O'Connor drilled a shot wide, Niall Morgan saved a Stephen McAlorum effort and Ryan Harpur fired just wide.
On 59 minutes Mark Burns allowed the ball to drop into the path of Lavery who ran and scored from an acute angle.
Lavery picked the ball up after a long kick from Morgan.
Celtic almost equalised in the 79th minute, but Paul McVeigh's shot was pushed round the post by Morgan.
Robert Robinson made a fine save to deny Michael Ward after 84 minutes.