Dan Biggar’s boot and a Richard Fussell try ensured the Ospreys led 13-6 at the interval. And they put the result beyond doubt with a penalty try and a touchdown from Richard Hibbard on his 100th appearance.
To rub further salt into the wounds Munster saw Damien Varley sent-off in the closing stages.
The victory sees the reigning RaboDirect PRO12 champions climb the league table following their difficult start to the season.
Biggar fired the hosts into an early lead with a pair of penalties at the Liberty Stadium.
The Ospreys continued to dominate affairs on the scoreboard and Fussell crashed over the whitewash after a powerful break from Andrew Bishop.
Biggar expertly slotted the touchline conversion to put the Swansea-based outfit a commanding 13-0 lead.
Munster however, began to build their way into the game and O’Gara knocked over his side’s first points on 24 minutes.
Some colossus defence from the home side denied Munster a crucial try following a sustained period of pressure, but O’Gara cut the Ospreys lead to 13-6 at the break.
O’Gara quickly got the scoreboard ticking following the restart, after Ryan Jones was penalised at the breakdown, to reduce the deficit to four points.
But Munster’s flying start to the half brought to a halt when Tommy O’Donnell was sent to the sin-bin for pulling down a powerful maul and Biggar slotted the penalty.
The Ospreys swifly made Munster pay for their indiscipline. They launched wave after wave of attacks and after being awarded a five-metre scrum they made the weight of their numerical advantage count with a penalty try.
Ian Keatley hit-back with a penalty but the Ospreys instantly responded with their third try, through Hibbard, to put the result beyond doubt.
Munster continued to battle but their frustrations boiled over when Varley was sent off for retaliation.
