Speaking after the game, a satisfied Holley said: "The character the players showed was probably the most pleasing, obviously they've taken a bit of stick but they've stuck at it all week.
"Clearly we've got a lot of talent. We're working on some new things, we saw it come to fruition a bit more tonight and I think as the season goes on we'll hopefully get better and better.
"We want to attack as much as we can with the players we've got in large numbers, using backs and forwards and we saw a bit more of that tonight and got our rewards."
The Ospreys management made 11 changes - two positional - to the team that went down to Leinster at home. Most notably, James Hook was switched to the centre and Tom Smith move to the blindside of the scrum, while openside Steve Tandy was handed his first start of the season.
Unbeaten at Firhill since April, Glasgow gave a first start to summer signing McCall as coach Sean Lineen reversed all six of the changes he made for last weekend's trip to the Dragons.
The only difference from the line-up that recorded victories over Munster and the Scarlets at Firhill in the opening fortnight of the league was McCall's inclusion ahead of Peter Murchie.
McCall's centre partner Graeme Morrison made his presence felt early on, producing a big hit off the kick-off and an offence in the first scrum allowed Parks kick the hosts into the lead.
After a good run from Rob Dewey and a ruck infringement from Tandy, the Warriors doubled their advantage thanks to Parks' second penalty.
Pressure from the Ospreys in the scrum set up field position and though the attack stalled somewhat, young number 10 Dan Biggar popped over a drop goal to get his side on the scoreboard.
Parks was off target with a drop goal attempt himself before the Ospreys countered well, gaining yards through scrum half Mike Phillips and the pumped-up Jones.
A resultant penalty was smacked through the posts by Biggar, bringing the sides level at 6-6 after 16 minutes' play.
A long scoreless spell followed, the best of the chances falling to Ospreys flyer Shane Williams and Glasgow's Morrison.
But the first real twist arrived six minutes before the break when Glasgow engineered a try for Scotland Sevens international McCall.
Big winger Dewey was hauled down just short of the try-line, having made 55 metres on a powerful run through the middle of the Ospreys defence.
Glasgow managed to recycle the ball quickly, Parks' cross-field kick was caught by Kelly Brown over Shane Williams and he passed back inside for McCall to run in the try.
Parks nailed the conversion and added a drop goal to increase the lead to 16-6, with Biggar missing a long range penalty at the other end.
Glasgow were full value for their lead but the Ospreys roared back at them, scoring 17 points in a devastating seven-minute spell.
Biggar's second penalty success saw the Welshmen open the second half on a good note, but they suffered a setback when Parker was yellow carded for a shoulder charge.
Glasgow looked to have a solid platform, with an advantage on the scoreboard and a numerical edge on the pitch - however, Holley's charges soon began to boss things up front and some quality finishing saw them hit the front for the first time.
Lee Byrne linked with Bowe in a move which almost led to a try, but the latter turned on the style some minutes later to make the line.
There were a number of players involved in the build-up, Phillips creating the go-forward off the back of a retreating scrum and Bowe was there to finish it in terrific fashion by taking Parks on the outside shoulder and scooting over, with Biggar converting.
A subsequent penalty from Biggar nudged the Ospreys ahead at 19-16 and Walker, on in place of Parker, scored from close range on 64 minutes to tighten the visitors' sudden grip on the game.
Bowe moved to the centre and Walker was able to barge past McCall and Dewey to cross the whitewash. Glasgow were annoyed by a possible case of obstruction in the build-up to the try, but the score stood and Biggar again converted to stretch the margin to ten points.
Thom Evans managed to forced Byrne into a hurried clearance as Glasgow tried to hit back, but try scorer Walker covered well and the Ospreys, marshalled superbly by man-of-the-match Ryan Jones, held firm for an important win.
The result continued Glasgow's poor record against the Ospreys - the Scottish side have now won only two of their last eleven meetings with the Liberty Stadium residents.
|Glasgow Warriors Score Card|
|Ospreys Score Card|