Nick Robinson put himself in contention for a Wales start against Italy a week on Saturday by inspiring Cardiff Blues to a bonus-point win at the Arms Park.
Blues (21) 40:
Tries: N Robinson, Czekaj (3), J Robinson
Cons: N Robinson (3)
Pens: N Robinson (3)
Ospreys (9) 14:
With first-choice Stephen Jones a doubt with injury, fly-half Robinson kicked 15 points, scored a try and created the first of three scores for Chris Czekaj.
Jamie Robinson scored the Blues' fifth try, as the Ospreys managed just one from captain James Bater.
Shaun Connor scored two drop-goals and Gavin Henson a penalty for the Ospreys.
The Ospreys penalty count was nearing double figures by the time Robinson had slotted over his third penalty inside the opening quarter.
Connor's second drop-goal closed the gap to 9-6, but the Blues pulled clear again on the half hour as Robinson sliced through an undisciplined defence.
The fly-half picked up the ball on the halfway line from a Blues line-out and had a clear run to the line after brushing off Steve Tandy's weak tackle.
Robinson, who added the conversion, almost created another try 10 minutes later with another clean break, but winger Craig Morgan knocked-on under pressure with the try-line in sight.
There was no let up for the visitors though as Jamie Robinson took inspiration from his brother to launch an attack deep from inside his own half in first-half stoppage time.
The ball eventually reached the fly-half just outside the Ospreys 22, and his perfectly weighted chip-kick to the right corner was collected by Czekaj for the Blues' second try.
Chris Czekaj scored three well-taken tries for the Blues
The Ospreys emerged for the second half with a full compliment having lost prop Cai Griffiths to the sin-bin before the break, but their slack defence was soon exposed by the Blues backs once again.
Centre Marc Stcherbina was the architect this time, and after Rhys Williams passed to Czekaj the winger had enough pace and strength to fend off Shane Williams to dive over in the right corner.
The Ospreys needed a quick reply and captain Bater led by example as he outmuscled the home defence to score from a simple catch-and-drive line-out move to make it 26-14.
But two converted Blues tries in four minutes put the result beyond doubt with 25 minutes to go.
Williams combined well with Czekaj for the winger to complete his hat-trick, and then Jamie Robinson scored in the same corner after the Ospreys defence was all at sea again.
An awful evening for the Ospreys was compounded in injury-time when lock Andy Newman was sin-binned after denying what looked like a certain Blues try.
Blues coach Dai Young:
"I thought we played all the rugby and I thought our finishing was clinical.
"Our approach work throughout the season has been good, but once we get into the opposition 22 we seem to panic and lack self-belief.
"We've worked on that over the last couple of weeks and performances like this are only going to add to the confidence."
Ospreys coach Lyn Jones:
"Conceding those seven points just before the break was a little bit too much for us, but we dropped our heads far too early.
"We refused to stand up. Failure is not to be knocked down, it's the refusal to get back up.
"I'm desperately sorry we didn't show any character or bottle. It's shocking. It's up to the players to perform."
Blues: Williams (capt); Morgan, J. Robinson, Stcherbina, Czekaj; N. Robinson, Phillips; Yapp, Goodfield, Jenkins, D. Jones, Goode, Molitika, Sowden-Taylor, Rush.
Replacements: L. Thomas for Stcherbina (78), R. Powell for M. Phillips (72), M. Jones for Yapp (71), Johnson for Goodfield (74), Quinnell for Goode (61), Schubert for Molitika (73). Not Used: Macleod.
Ospreys: Henson; Terblanche, S. Parker, A. Bishop, S. Williams; Connor, Spice; Griffiths, Hibbard, Millward, Newman, Evans, Bater (capt), Tandy, Thomas.
Replacements: M. Jones for Connor (65), Roberts for Spice (65), Bennett for Hibbard (51), Bateman for Evans (59), D. Dillon for Tandy (59). Not Used: Mitchell, Mustoe
Referee: Tim Hayes (Wales)