In truth, the scoreline flattered the Iron who scored two goals in the final few minutes.
David Mirfin headed the Iron into the lead in the first-half, before Sam Winnall and Deon Burton added gloss to the score-line.
Andy Welsh thought he had made it two midway through the second half powering a Hawkridge cross goalwards, only for the linesman to have deemed the ball did not cross the line.
Grimsby had a penalty claim turned down by referee Darren Drysdale with five minutes to go when Aswad went down in the area before the Iron struck twice to confirm a semi final date against Lincoln.
Man of the Match Terry Hawkwidge, who dropped in expertly at right back following Andy Dawson picking up a knock to the thigh found substitute Winnall, who powered a firm header into the corner of the net to make it 2-0. Then with just moments left, the Grimsby players turned to the referee appealing for a free kick which never came and were caught motionless as Deon Burton launched an effort from the half way line, that flew over goalkeeper McKeown into an empty net.