Biggar made amends for his earlier miss by adding the conversion to make it 7-0.
Eifion Roberts (Sale), Dan Biggar (Ospreys), Martin Roberts (Scarlets), Powell and Halfpenny were called up.
Wales boss Warren Gatland says Priestland's running ability earned him the nod over Osprey Dan Biggar.
BBC: Rhys Priestland hails John Muggleton's role in his rise
But the Ospreys already have James Hook, Gareth Owen and Dan Biggar in that position.
Biggar added his third penalty with five minutes remaining to effectively seal an Ospreys win.
Stand-off Dan Biggar crossed the line and kicked with accuracy to give the visitors a 13-3 lead.
Sexton was successful with three of his four second-half penalty attempts, with Biggar kicking a penalty for Ospreys.
Biggar was again on target with the conversion to give his side a 14-3 lead at the interval.
His elusive run freed Lamont and the Scottish full-back eased past Biggar to dive over in the corner.
Blues full-back Blair landed two easy penalty kicks either side of a Dan Biggar reply for the Ospreys.
Ospreys had matched Edinburgh's tally of four tries, but James Hook and Dan Biggar both missed crucial kicks.
Biggar then kicked his fourth shot at goal from four attempts after Bryan Young was penalised at a scrum.
Fly-half Biggar then chipped over the top of the visitors' defence, Hook gathering and seeing the ball quickly recycled.
Dan Biggar, Martin Roberts, Morgan Stoddart and Eifion Roberts drop out of the squad from the autumn Test series.
Biggar missed with a kick at the posts four minutes later as both sides struggled to gain the ascendancy.
Biggar dropped a goal in the 54th minute and added a penalty when Alan Quinlan transgressed at a ruck.
The flints were unearthed in a ploughed field near Biggar in South Lanarkshire.
Centre Andrew Bishop hacked the ball on for Dan Biggar, who also kicked 16 points, to get Ospreys' second try.
Ospreys scored the first try of the game when Richard Fussell offloaded to Biggar who crossed the line with ease.
Moments after Biggar missed the conversion, replacement Leigh Halfpenny, on for the injured Blair, almost replied instantly for the hosts.
Peel and Nicky Robinson replace Gareth Cooper and Dan Biggar at half-back while Mark Jones takes Chris Czekaj's wing spot.
"I'm sure the coaches will have pinpointed a few areas for improvement, " said Biggar after their thrashing of the Scarlets.
Biggar's excellent conversion tied the scores, but Ulster crept ahead again after Cave shook off Marty Holah for an unconverted score.
Tommy Bowe raced over for the Ospreys' first try in the 19th minute, with Dan Biggar converting to make it 7-0.
Biggar crossed the home side's line after two minutes but referee Chris White had already blown up for a forward pass.
Parker crossed for a second time in the 78th minute and Hook's replacement, Dan Biggar, converted to round off the win.
Biggar added the simple conversion to put the Ospreys five points clear.
The club have nurtured more than 200 Scottish international players, including Gavin Hastings, Damian Cronin, Mike Biggar, Al McHarg and Kenny Logan.
BBC: SPORT | Rugby Union | Scottish | London Scottish academy launched
Biggar's Munster rival Ronan O'Gara scored a try and kicked two penalties.
The Ospreys also have Andrew Bishop, Dan Biggar, Tom Prydie, Kristian Phillips and Ian Gough available to face Edinburgh at Murrayfield on Sunday.
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