The hosts kept alive their impressive home record and made the perfect start as they took advantage of a disorganized visitors defence when USA Eagles wing, Taku Ngwenya, crashed over for a try after only five minutes.
Full back Iain Balshaw then split the Ospreys defence to create another opportunity finished off by Ngwenya who crossed over for his second try despite the attention of Tommy Bowe.
Scrum half Dimitri Yachvili added his second conversion and a penalty to give the home side a well deserved 17-0 lead at half-time against a Welsh side which struggled to launch a meaningful attack.
The visitors lost replacement scrum-half Kahn Fotuali to a yellow card and were down to 14-men for the first ten minutes of the second half and Biarritz took full advantage when wing Benoit Baby crossed for Biarritz’s third try.
Balshaw was the next to take advantage of their extra-man and crossed for Biarritz fourth try for the bonus point before replacement Richard Hibbard barged his way over for the Ospreys try.
Wing Ngwenya then rubbed salt into the Ospreys wounds with a third try to make it a hat-trick of tries for the American midway through the second half to seal a one-sided victory against the Welsh side.
