The uncertain future for Welsh rugby, with the regions yet to meet the WRU's end-of-year deadline to recommit to their participation agreement, hung over the first of the holiday derbies, but a decent crowd defied a treacherous weather forecast to attend.
The Blues went into the game boosted by their Heineken Cup double over Glasgow, but the Ospreys could take heart from the fact that they completed a PRO12 double over the capital city outfit in each of the past two seasons.
After an early Leigh Halfpenny penalty had put the home side ahead, the Ospreys quickly drew level in bizarre fashion. A poor pass from young scrum-half Tom Habberfield flew high and wide of Biggar, who stretched, but could only knock it backwards.
The Wales fly-half then turned, grabbed the loose ball, and calmly slotted over a drop goal.
The Blues were lucky to avoid conceding a try after both half-backs had clearance kicks charged down, but a Biggar penalty gave them the lead before Halfpenny, of all people, totally mis-hit a simple effort from in front of the posts.
Biggar, who scored all of Ospreys' 55 points in their European group, promptly showed Halfpenny how it was done.
It was no use and Halfpenny missed again, although this time the swirling wind at the River Taff end was largely responsible. But the BBC Sport Personality of the Year runner-up made amends with a storming run from inside his own half which led to a try for hooker Kristian Dacey. This time Halfpenny put the ball firmly between the posts.
After opting to go for a fruitless lineout from their next penalty, the Ospreys decided to take the points when French referee Jerome Garces continued to clamp down on Blues illegalities and two more Biggar kicks put the visitors into an interval lead.
Halfpenny cut the deficit early in the second period, but the Ospreys piled on the pressure and flanker Justin Tipuric found a gap to dart over, Biggar judging the wind perfectly with the conversion.
Halfpenny also ignored the conditions with a penalty from halfway and there was a further blow for the visitors when replacement prop Marc Thomas was sin-binned following a collapsed scrum.
The Ospreys promptly conceded another Halfpenny penalty, but survived the rest of the punishment and were able to maintain their three-point advantage until the final whistle.