Thorniewood took the lead after 14 minutes when brilliant work down the left wing by Dillon McLauchlan set up Declan Brown, who turned a defender inside out and scored for 1-0.
Declan McDonald’s header for Benburb levelled the game after 75 minutes before ’Wood went 2-1 up with eight minutes remaining when Steven Seaton fired home from an acute angle.
But the Viewpark team were sickened in the final minute when Bens’ Lewis McTaggart shot home through a crowd of players from 10 yards.
However, penalty goals by Frazer Stobie, Ally Small, Declan Brown and Jack McClair then won the resultant shootout for ’Wood, with Forbes saving a Bens penalty and the hosts sending another spot kick off target.
"It was gut-wrenching to lose a goal so late,” said Thorniewood secretary Eddie Lynas. "And our goalkeeper injured his ankle after a collision in the run up to it.
"There’s nothing worse than a goalkeeper who’s injured going into a penalty shootout but he stood firm.
"This cup run is incredible. We are not the biggest of teams but what we’ve got is a great work attitude.
"They all work for each other, they all play for each other and they don’t give up.
"We were up against a big team with a lot more experience in them and obviously with a lot more money than we have."
On the fact that last weekend’s win saw ’Wood beat a third top flight side on their way to the last eight, Lynas added: “Benburb were a big, strong, physical team who are mid-table in the Premiership. “And they can pass the ball about well.
"But our boys applied themselves well. Our back four defended superbly and when called upon our goalkeeper proved his class.
"We fully deserved to win. I spoke to a couple of Benburb men after the game and they said we were the better team on the day and they were lucky to make it 2-2.”
’Wood’s Killie Pie Cup quarter-final will see them host Kilwinning Rangers – who are fifth in the West of Scotland Premier Division – on Saturday, May 21.
"We are confident but not over confident,” Lynas said. “On our day we can compete with the best I think.”
Thorniewood United’s charity golf day will take place at Bellshill Golf Club from 8.30am this Sunday in aid of the Billy McNeill charity.
A total of 45 teams are taking part in the Texas Scramble fourball with room for a few more. Entry is £100 per four-man team.
If interested, email [email protected]