A goal in each half, the latter in the 91st minute, sends Institute into the North West Senior Cup Final where they will meet Limavady.
Harry McConkey made 8 changes from Saturday's starting line up allowing others to get valuable minutes under their belts.
The Mallards did have a penalty shout turned away in the first half whilst both sides also managed to hit the post. Nathan Cashel also had a great chance to equalise late in the game when one on one with the Stute keeper, but he made a good stop.
Best wishes to Institute in the Final.