Munster are just two points away from the Magners League title after the Ospreys crashed to a 32-30 home defeat to Edinburgh in the Magners League on Saturday.
The Ospreys included five of their six Lions - Shane Williams, Mike Phillips, Lee Byrne, Tommy Bowe and Adam Jones - with Alun Wyn Jones rested.
Edinburgh have no Lions representatives as yet but captain Mike Blair would have been looking to impress after Munster's Tomas O'Leary was ruled out of the tour to South Africa after suffering a broken ankle against the Scarlets on Friday night.
The match was not three minutes old before Williams, celebrating his 100th appearance in an Ospreys shirt, produced a jinking run towards the Edinburgh 22 as the home side enjoyed a positive start.
And a useful start was turned into a 10-0 lead on 14 minutes with tries for Lions wing duo Williams and Bowe.
Williams cruised in for the opening try on 10 minutes, sent away by a James Hook outside pass from a line-out.
And another set-piece, this time a scrum, produced a try for Bowe, who went over in the right corner after being put in by Byrne.
Edinburgh responded with a fine try for centre Ben Cairns made from a break by outside-half Godman.
Byrne attempted a long-range penalty from the halfway line on 25 minutes but he was well short with his effort, as was Dan Biggar with an easier one from the 22.
And on 31 minutes the Ospreys had a third try ruled out when flanker Steve Tandy went in at the right corner.
The Ospreys rued their missed opportunities as Edinburgh scored two tries in the space of as many minutes to open up a 19-10 lead. First Cairns went in for his second try before Simon Webster was on the end of a cross kick to go over in the left corner.
But the Ospreys recovered to cut the interval deficit to 19-17 with a try for Byrne, who was sent in by Lions team-mate Bowe.
Edinburgh drew first blood in the second half with two Paterson penalties extending their lead to eight points.
Against the run of play the Ospreys surged back into the lead with a converted try from hooker Huw Bennett to seal a bonus point, and two penalties from Biggar helped turn a 25-17 deficit into a 30-25 lead in the space of seven minutes.
But the Ospreys were made to defend in the closing stages and were not helped by losing a line-out which led to Edinburgh's fourth and decisive try, with Phil Godman landing a nerveless last-gasp conversion.
For the Ospreys:
Tries: Williams, Bowe, Byrne, Bennett
Cons: Biggar 2
Pens: Biggar 2
Tries: Cairns 2, Webster, Kelly
Cons: Paterson 2, Godman
Pens: Paterson 2
Ospreys: 15 Lee Byrne, 14 Tommy Bowe, 13 James Hook, 12 Andrew Bishop, 11 Shane Williams, 10 Dan Biggar, 9 Mike Phillips, 8 Ryan Jones (c), 7 Steve Tandy, 6 Tom Smith, 5 Andy Lloyd, 4 Filipo Levi, 3 Adam Jones, 2 Huw Bennett, 1 Paul James.
Replacements: 16 Ed Shervington, 17 Duncan Jones, 18 Ian Gough, 19 Marty Holah, 20 Tavis Noyle, 21 Jonathan Spratt, 22 Jonny Vaughton.
Edinburgh: 15 Chris Paterson, 14 John Houston, 13 Ben Cairns, 12 Nick De Luca, 11 Simon Webster, 10 Phil Godman, 9 Mike Blair (capt), 8 Allister Hogg, 7 Alan MacDonald, 6 Scott Newlands, 5 Jim Hamilton, 4 Craig Hamilton, 3 Geoff Cross, 2 Ross Ford, 1 Kyle Traynor.
Replacements: 16 Andrew Kelly, 17 Ryan Grant, 18 Scott MacLeod, 19 Matt Mustchin, 20 Greig Laidlaw, 21 David Blair / Andrew Turnbull, 22 Hugo Southwell.
Referee: Alain Rolland (Ireland)
Touch judges: Huw David (Wales), Simon Harris (Wales)
Television match official: Tony Rowlands (Wales)