Two of the weekend's ties ended level, but the draw for the semi-finals at Ravenhill was still made.
On Monday, February 28 either Armagh Royal or RBAI will face Coleraine Institution, while two days later either Campbell College or Methodist College will play Ballyclare High.
There was an exciting finish at Armagh, where the home team had a 14-6 lead with eight minutes left, but rbai dug deep to earn a 14-14 draw and a replay. It was a similar situation at Belmont, where Campbell College fought back from a 10-0 half-time deficit, after two first-half Methody tries, to justly earn a replay at Pirrie Park on Wednesday.
Ballyclare High came to Sullivan Upper as favourites and deserved their 37-29 success.
Sullivan had an Oliver Loughead try converted by Ross Adair, but the visitors stormed back with 27 points before half- time.
In the other tie Coleraine eliminated BRA 7-0. The winners defended well and were rewarded with a Patrick Farrell try, converted by Michael Poskitt.