Over 15,000 tickets have been sold for this match but there is still limited availability at www.ulsterrugby.com/buytickets. Alternatively, tickets can be purchased on the gate from 1.30pm on Saturday.
Pienaar will make his first appearance of 2017, having recovered from a knee injury sustained in the New Year's Eve fixture away to Leinster. The South African will partner Pete Nelson at half-back, with the latter successfully coming through the full 80 minutes in last weekend's victory over Edinburgh, following a 14-month layoff.
Gilroy, who shone with a 14-minute hat-trick for Ireland versus Italy, will join Bowe and Louis Ludik, one of Ulster's four try-scorers versus Edinburgh, in the back three.
Luke Marshall comes into the side at outside centre, meaning Darren Cave shifts inside to occupy the number 12 jersey.
Up front, Callum Black will start at loosehead prop alongside John Andrew and Ricky Lutton in the front row, while Pete Browne and Franco van der Merwe will renew their second row partnership.
Marcell Coetzee, who put in a hugely impressive debut for Ulster last week, retains his starting berth at number 8, with Sean Reidy and Chris Henry playing in the other loose forward positions.
Club captain Rob Herring has suitably recovered from injury to take up a place among the replacements along with fellow forwards Andy Warwick, Wiehahn Herbst, Kieran Treadwell and Robbie Diack.
Hughes Insurance Ulster Academy player Jack Owens, who has featured at wing and full-back for the Ulster A team in this season's British & Irish Cup, is in line to make his senior debut if called upon. Paul Marshall and Jacob Stockdale will provide the additional backline cover from the bench.
Ulster team & replacements to play Glasgow Warriors, Guinness PRO12, Saturday 18th February, Kingspan Stadium (3.00pm kick-off):
(15-9): L Ludik, T Bowe, L Marshall, D Cave, C Gilroy, P Nelson, R Pienaar;
(1-8): C Black, J Andrew, R Lutton, P Browne, F van der Merwe, S Reidy, C Henry (C), M Coetzee;
Replacements (16-23): R Herring, A Warwick, W Herbst, K Treadwell, R Diack, P Marshall, J Stockdale, J Owens.