PRO12 holders Glasgow Warriors handed the Ospreys their fifth defeat out of six games on Sunday as they won 31-19 at Scotstoun Stadium.
The match was a war of attrition, especially in the first-half, the rustiness of both sides with several returning World Cup stars on the pitch showing through.
Glasgow players in particular were guilty of committing handling errors on multiple occasions. Meanwhile, two sin bins for Ospreys at the start of the first half turned the match in the hosts' favour. Josh Matavesi and Ryan Bevington were both carded in close succession to leave the Welsh side with 13 men on the pitch at one point.
This result condemned the visitors to their fifth defeat in six matches so far this season. In contrast, this will be seen a turning point for Glasgow. Last season's champions producing an effective display to earn their third victory of the season.
The first chance at goal went the way of the hosts in the second minute, Duncan Weir scoring the penalty to give the hosts a three point lead.
Dan Biggar levelled the scores for the visitors four minutes later with a beautifully struck penalty from close to the half-way line.
Biggar put his side into the lead with another long range penalty in the 13th minute.
It took sixteen minutes for the scoreboard to be threatened once more. Sean Lamont rode two tackles out wide before going over for the first try of the match, putting the hosts into the lead.
Weir scored a penalty for the home side in the 43rd minute to yet again take the lead but Biggar then responded immediately with a penalty of his own.
Two minutes later Matavesi was sent to the sin-bin for holding on in the ruck. Glasgow took advantage in the 50th minute, Weir crossing the whitewash following a spell of sustained pressure for the Warriors. The Scotland international also converted the try to hand his side a six point lead.
Weir added another three points in the 55th minute to give his side a commanding buffer.
Things got even worse for the Ospreys as they found themselves with another man in the bin in the 57th minute. Replacement Bevington leaving his side with 13 men, yet again for holding on in the ruck.
Glasgow scored their third try of the match in the 63rd minute, Alex Allan finally finding a gap in a spirited Ospreys defence to put the home side into a 14 point lead.
Ospreys scored a late try in the 73rd minute through Dan Baker before Taqele Naiyaravoro earned the home side a bonus point with a fourth try in the final minute of the match.
Tries: Lamont, Petersen, Allan, Naiyaravoro
Pen: Weir 3
Pen: Biggar 4
Glasgow: 15 Tommy Seymour, 14 Lee Jones, 13 Richie Vernon, 12 Peter Horne, 11 Sean Lamont, 10 Duncan Weir, 9 Mike Blair, 8 Ryan Wilson, 7 Simone Favaro, 6 Rob Harley (c), 5 Leone Nakarawa, 4 Greg Peterson, 3 Sila Puafisi, 2 Pat MacArthur, 1 Gordon Reid.
Replacements: 16 James Malcolm, 17 Alex Allan, 18 Zander Fagerson, 19 Scott Cummings, 20 Chris Fusaro, 21 Ali Price, 22 Sam Johnson, 23 Taqele Naiyaravoro.
Ospreys: 15 Dan Evans, 14 Tom Grabham, 13 Ben John, 12 Josh Matavesi, 11 Eli Walker, 10 Dan Biggar, 9 Brendon Leonard, 8 James King, 7 Justin Tipuric, 6 Dan Lydiate, 5 Rory Thornton, 4 Lloyd Ashley (c), 3 Aaron Jarvis, 2 Scott Baldwin, 1 Paul James.
Replacements: 16 Scott Otten, 17 Ryan Bevington, 18 Dmitri Arhip, 19 Alun Wyn Jones, 20 Dan Baker, 21 Tom Habberfield, 22 Sam Davies, 23 Jonathan Spratt.
Referee: Peter Fitzgibbon (Ireland)
Assistant referees: Lloyd Linton (Scotland), Mike Adamson (Scotland)