A fast-paced opening few minutes saw both sides showcasing their skills with ball in hand, but Ulster drew first blood when Ruan Pienaar punished the Ospreys for the tackler not releasing. The South African made it 3-0 - taking his personal tally to 66 points in the last five games.
The visitors then produced a good passage of play and won a penalty after Ulster's Lewis Stevenson booted the ball away from a ruck. Matthew Morgan levelled it up at 3-3.
The Welsh side, missing 16 players through injury and Six Nations representatives, were playing at a frantic pace and dominating possession but poor discipline - going in off their feet at the breakdown - allowed Pienaar to extend Ulster's lead to 6-3.
Again the Ospreys came back at Ulster, but after numerous phases they gave away a penalty at the critical moment, five metres away from the try-line. Their efforts were not totally in vain, Morgan squaring the match again at 6-6 with a penalty after 21 minutes.
Another marathon of 15 attacking phases followed for the Ospreys but they couldn't breach Ulster's defence and the home side cleared their lines, and started to enjoy more of the ball.
Paddy Wallace made a scything break which led to another Ulster penalty, again the Ospreys not rolling away on the deck and Pienaar made them pay, making sure his side went into half-time ahead 9-6 despite the Ospreys having the lion's share of possession and being more adventurous in attack.
Alun-Wyn Jones made his return from a three-month-long shoulder injury, coming off the bench after half-time. The 67-cap lock entered a game that had lost none of its pace since the first half.
Ospreys again took charge with the ball but it was proving energy-sapping trying to break through the Ulster defence for a try. Last year's RaboDirect PRO12 champions eventually settled for another penalty to draw level at 9-9 through Morgan.
Ulster came back at the Ospreys, producing wave after wave of attack. Pressure told and a sin-binning for Ospreys No.8 Morgan Allen followed when he failed to release a tackled player. Debutant fly-half Stuart Olding got his first league points to edge Ulster ahead 12-9.
Out of nowhere, the Ospreys scored a superb breakaway try finished by the most unlikely of players. A break from centre Tom Isaacs was finished by prop Bevington who ran in from the ten metre line, chased all the way by Ulster's outside backs. Morgan converted to make it 12-16 with ten minutes left.
Ulster, chasing the win, threw caution to the wind in a frantic and tense last five minutes.
But it wasn't enough and despite a nervous last few moments, the Ospreys managed to get the ball out of play and record a huge win away from home against the league leaders.
|Ulster Rugby Score Card|
|Ospreys Score Card|