Despite a thrilling first-half performance that earned the visitors a consolation bonus point, hooker, Grobbelaar grabbed a treble as the South African province run in nine tries to Ospreys six.
Mark Jones’ side had led 26-19 at the break after running in four tries in a breathless opening.
Wing, Keelan Giles opening the scoring from the get-go after Phil Cokanasiga’s line break found Jack Walsh to put the Welsh speedster over down the left, before centre Kieran Williams crossed twice in quick succession.
Full-back Walsh added another after a clever offload by Harri Deaves, with Dan Edwards converting three to give the visitors a shock advantage at Loftus Versfeld.
The Bulls though would respond through veteran flanker Marcell Coetzee’s double, whilst Grobbelaar’s first would help the home side stay in touch at the break.
Johan Ackermann’s side, however, would be a different beast after the break, overwhelming the Ospreys with a second 40 display of sheer power and pace.
Grobbelaar capping a fine individual performance, adding two more from the driving maul either side of a blistering finish by wing Cheswill Jooste, whilst centre Jan Serfontein and replacement hooker Juann Else also crossed.
Jooste’s second try in the final minutes adding gloss to an outstanding showing from the South Africans.
Ospreys, to their credit, in the intense and humid conditions, kept the scoreboard ticking over, with number eight Morgan Morse crashing over midway through the second-half, whilst Giles grabbing his second late on.
Jones’ side, hampered by a yellow card for lock James Fender, could not stem the tide as the Bulls raced past the half-century despite missing several of their Springboks contingent.
Ospreys will now look to bounce back as they remain in South Africa for a clash against the Stormers on Friday before facing off against Zebre Parma and Glasgow at Bridgend’s Brewery Field.
Ospreys XV:
Walsh; Kasende, P Cokanasiga, K Williams, Giles; Edwards; Morgan-Williams; G Phillips, Lake (captain), T Botha, R Davies, Fender, Moriarty, Deaves, Morse.
Replacements:
E Lewis, S Thomas, R Henry, Sutton, Ratti, L Davies, Florence, Houston.
Bulls XV:
D Williams; Jooste, Kriel, Serfontein, Isaacs; Johannes, Papier; Shekwani, Johan Grobbelaar, Smith, Jaco Grobbelaar, van Heerden, Coetzee (capt), Gumede, van der Westhuizen.
Replacements:
Else, Swart, Klopper, C Wiese, Xaba, de Wet, Vorster, Gans.
[Lead image: Ospreys Rugby]
