Rory Best will again captain the side, with props Callum Black and Ricky Lutton, and second rows Pete Browne and Franco van der Merwe joining him in the front five. The back row trio of Iain Henderson, Chris Henry and Sean Reidy, which performed so effectively last week, is also retained.
Man of the Match in that game, Ruan Pienaar, will line out alongside Paddy Jackson at half back, with Stuart McCloskey and Luke Marshall continuing their midfield partnership. Gilroy, Andrew Trimble and Jared Payne complete the backline.
The bench, which helped to deliver a strong second half performance last weekend, is also unchanged. Rob Herring, Kyle McCall, Andy Warwick, Robbie Diack and Roger Wilson cover the forward positions, while Paul Marshall, Stuart Olding and Darren Cave are included as backline options.
A bonus point win on Saturday would guarantee Ulster a play-off spot, and also give them an outside chance of that game being in Belfast. Anything less and they will be looking at other results to confirm their place in the last four, although fellow contenders Scarlets face a difficult trip away to Munster.
The Ulstermen's only defeat in the last five rounds of the Guinness PRO12 was at Glasgow in Round 18. They will face an in-form team who have won their last three matches, all with maximum points. The Welshmen require a victory to give themselves any chance of acquiring a Champions Cup spot for next season.
The match will be televised live on Sky Sports and on BBC Northern Ireland.
Ulster team and replacements to play Ospreys, Guinness PRO12, Saturday 7th May, Liberty Stadium (kick-off 3pm):
(15-9): J Payne; A Trimble, L Marshall, S McCloskey, C Gilroy; P Jackson, R Pienaar;
(1-8): C Black, R Best (c), R Lutton, P Browne, F van der Merwe, I Henderson, C Henry, S Reidy;
Replacements (16-23): R Herring, K McCall, A Warwick, R Diack, R Wilson, P Marshall, S Olding, D Cave.
Referee: Marius Mitrea (FIR, 52nd competition game)
Assistant Referees: Leighton Hodges, Gwyn Morris (both WRU)
Citing Commissioner: Dennis Jones (WRU)
TMO: Derek Bevan (WRU)
Guinness PRO12 Ulster News
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