James Hook caught the eye from the Ospreys' midfield
Ospreys 30 (3)
Tries: S Terblanche, T Selley, A Wyn Jones.
Cons: J Hook 3.
Pens: J Hook 2.
DG: S Connor.
Reivers 13 (13)
Tries: K Brown.
Cons: S Jones.
Pens: S Jones, G Law.
A largely second-string Ospreys side still proved too strong for Border Reivers at the Liberty Stadium.
The Scots led 13-3 at half-time thanks to Kelly Brown's early try, two kicks from full-back Steve Jones and another long-range effort from wing Garry Law.
But Ospreys, inspired by James Hook and reinforcements off the bench, hit back.
Stefan Terblanche, Tal Selley and Alan Wyn Jones all added second-half tries, while Hook finished with 12 points and the man-of-the-match champagne.
The result proved there is some strength in depth at the Ospreys, who were forced to dig deep into their reserves as they played their second game in 48 hours.
But the early signs were not promising for the Welsh region as Reivers romped into an early 10-0 lead.
Jones' penalty was swiftly followed by a try, created when Nick De Luca seemingly dummied the whole Ospreys backline.
The first half was very scrappy but we kept playing, cut down the errors, and it paid off in the end
The centre had four men in support to give the scoring pass to and chose blind-side flanker Brown, who loped over for five points that Jones improved to seven.
Reivers did not have it all their way as the Ospreys managed to mount some threat in the opposition's half.
But street-wise defence, allied with the Ospreys' general sloppy play, kept the Scottish line intact.
Hook managed to get the home side going with a penalty late in the half, but Law - summoned by Reivers skipper Chris Cusiter as his long-range kicking option - restored the 10-point lead.
Revitalised by their half-time break, and possibly an ear-bending from coach Lyn Jones, the Ospreys re-emerged to produce the best move of the match.
Hook scythed through midfield and Gregor Townsend's weak tackle, off-loading to Selley who showed great strength to stay upright and find Terblanche in support.
The former Springbok rounded the move off over the whitewash and Hook added the extras.
Sensing, perhaps, that the game was there for the taking, Ospreys coach Jones started to drip-feed some of his stars off the bench.
Justin Marshall, Jon Thomas and Gavin Henson all duly arrived on the pitch, but the standard of play - from either side - struggled to rise above mediocre.
Hook was still catching the eye with his running from inside centre, although the 21-year-old added the bread-and-butter of his trade with a 40-metre penalty to bring Ospreys level with 15 minutes left.
Reivers started to creak and then shipped the crucial try as they were caught short-handed down the blind-side.
Hook again sniffed the space and sent Selley, cutting a sweet inside line, darting under the posts to give his young provider a simple conversion.
Shaun Conner's late drop-goal moved the Ospreys two scores clear and denied the Scots even the consolation of a losing bonus point.
There was still time for a sin-binning from each side, Reivers back-row Ross Beattie caught throwing a punch and Mike Powell for dropping a knee into his tackled victim.
Finally Ospreys lock Wyn Jones gave the score-line some gloss by barging over deep into injury time, Hook - of course - stroking the conversion.
Ospreys back James Hook:
"I didn't play on Wednesday and was a bit disappointed, so I just wanted to get out there on the pitch.
"The first half was very scrappy but we kept playing, cut down the errors, and it paid off in the end.
"We came here to win, and that's what we did, and I was just happy to get out there and play."
Ospreys: Stefan Terblanche; Richard Mustoe, Tal Selley, James Hook, Jonathan Vaughton; Shaun Connor, Martin Roberts; Paul James (capt), Richard Hibbard, Andrew Millward, Alun Wyn Jones, Lyndon Bateman, Lee Beach, Steve Tandy, Andy Lloyd.
Replacements: Barry Williams for Hibbard (58), Cai Griffiths, Mike Powell for Beech (72), Jon Thomas for Lloyd (28), Justin Marshall for Roberts (48), Gavin Henson for Terblanche (56), Sonny Parker for Connor (76).
Reivers: Steve Jones; Garry Law, Nick De Luca, Ben MacDougall, Mark Robertson; Gregor Townsend, Chris Cusiter (capt); Gavin Kerr, Ross Ford, Bruce Douglas, Opeta Palepoi, Craig Hamilton, Kelly Brown, Scott Gray, Ross Beattie.
Replacements: Steve Scott for Ford (65), Ed Kalman for Douglas (74), Stuart Grimes for Hamilton (56), Andy Miller for Gray (55), Brendan McKerchar for Cusiter (39), Simon Danielli for Robertson (51), Dougie Flockhart.
Referee: David Keane (IRU).