It was top versus bottom and it looked like it as a brave but out-classed Borders side spent most of the first half standing under their posts watching Ospreys outside-half Shaun Connor kicking goals. The Scottish players regathered in the second spell as mistakes crept into the Ospreys's game, but they were never going to overturn a 24-point halftime deficit.
With four matches left, the Ospreys lead arch-rivals Munster by 12 points. The Irish province have two games in hand - including today's home match against Glasgow - but the Welsh region are now at short odds to finish on top.
The Ospreys went into the match without seven Wales internationals - including man of the moment Gavin Henson - but welcomed Duncan Jones back to the bench after a broken thumb ruled the talented prop out of the opening two rounds of the Six Nations. As well, Ospreys coach Lyn Jones gave promising 19-year-old centre Andrew Bishop a start, and his powerhouse defence was a highlight of the match.
Lock Andy Newman, who led the home side out on to the field after becoming the first man to play 50 games for the fledgling Ospreys, opened the scoring with a try near the posts after only five minutes. Backrower James Bater found a gap a mile wide in an already fragile-looking Borders defence and he slipped a clever pass to a rampaging Newman.
Connor added the extras and two close-range penalty goals before some good work from scrum-half Richard Rees gave Bater the space to dive over in the corner. Connor slotted the conversion from the sideline to give the Ospreys a 20-0 lead in as many minutes.
The Borders stemmed the flow - more out of good fortune than good play - and even troubled the scorers when centre Charlie Hore slotted a 40-metre penalty goal as Newman's 50th match ended with a knee injury and Ospreys prop Paul James also limped off.
James' injury resulted in Duncan Jones taking the field to a huge ovation, similar to the cheer three minutes later when flanker Richie Pugh showed his exceptional pace to out-sprint the covering defenders and score the Ospreys' third try. Connor didn't miss a goal all night and his conversion gave the home side a 27-3 lead at the break.
The Borders got the try they deserved when Hore found space 10 yards from the uprights, but the Ospreys were not to be denied a bonus point for four tries and prop Andrew Millward obliged in the dying minutes after a well-drilled rolling maul.
Ospreys: S Terblanche; D Tiueti (A Durstan 74), A Bishop, E Seveali'i, R Mustoe; S Connor (M Jones 79), R Rees (R Wells 74); P James (D Jones 37), B Williams (capt) (R Hibberd 78), A Millward, A Newman (L Tait 32), L Bateman, J Bater, A Lloyd, R Pugh (S Tandy 81)
Scorers: Tries - A Newman, J Bater, R Pugh, A Millward; Pens - S Connor 2; Cons - S Connor 4
Borders: G Morton; S Moffat, C MacRae, C Hore, N Walker; A Warnock, J Weston (I Wilson 73); T McGee (G Cross 71), R Ford (G Kay 76), B Douglas (capt), M Blair, C Stewart, J Dalziel, A Miller, W McEntee (K Brown 48)
Scorers: Try - C Hore; Pen - C Hore; Con - C Hore
Halftime: Ospreys 27-3
Referee: Colin Stanley (Ireland)