All three played in the international side's win over Georgia at the Aviva Stadium last weekend and return to Ulster to take on an Ospreys side unbeaten in the Guinness PRO12 and top of the division.
Olding starts at fullback with Gilroy named on the left wing in the only change to the side that beat Newport Gwent Dragons 23-6 at the start of the month. Louis Ludik completes the back three and is selected on the right wing.
Cave starts at outside centre, with Stuart McCloskey joining him in midfield at inside centre.
Paul Marshall and Paddy Jackson continue their partnership in the half backs.
Up front, Callum Black and Wiehahn Herbst start either side of Rob Herring in the front row, while Lewis Stevenson and Franco van der Merwe are paired in the second row.
Roger Wilson has recovered from a shoulder injury and starts at Number 8 with Sean Reidy selected at openside and Clive Ross named at blindside.
Nick Williams has recovered from the knee injury that kept him out of the win over Dragons and is in line to make his 50th appearance for Ulster if he is called upon.
Alan O'Connor is also selected among the substitutes as are fellow forwards John Andrew, Andrew Warwick and Declan Fitzpatrick.
Backs Michael Heaney, Ian Humphreys and Peter Nelson complete the match-day squad.
Ulster XV & Replacements to play Ospreys, Guinness PRO12, Kingspan Stadium, Friday 21st November, 19:35 (15-9): S Olding; L Ludik, D Cave, S McCloskey C Gilroy, P Jackson, P Marshall; (1-8): C Black, R Herring, W Herbst, L Stevenson, F vd Merwe, C Ross, S Reidy, R Wilson (Capt); Replacements (16-23): J Andrew, A Warwick, D Fitzpatrick, A O'Connor, N Williams, M Heaney, I Humphreys, P Nelson.
Guinness PRO12
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