The hosts outscored the Welsh club by nine tries to two, bagging the bonus-point in the 25th minute as they varied their play well and had the men in red under the cosh from the start, exerting pressure on attack and defence which led to a host of mistakes from the visitors.
The Vodacom Bulls were keen to keep the scoreboard ticking over and they scored five great tries in the first half, with the visitors struggling to keep up with their hosts’ intensity, pace and power, adding another four after the break.
Their intent was clear from the second minute, when Canan Moodie (wing) scored their first try from a move off the back of the scrum, and 12 minute later Coetzee and his fellow flanker Cyle Brink had added their names to the score sheet.
The hosts hammered their determination home in the 25th minute though, when Grobbelaar, the Vodacom Bulls' livewire hooker, went over for their bonus-point try from a move that started with a quick tap penalty in their own 22, moving the ball through the hands and leaving the Welshmen chasing shadows.
Elrigh Louw (No 8), who set up Moodie’s try with a great run, scored the fifth try after 30 minutes and although the visitors clawed one back, by replacement forward Sione Kalamafoni, it was scant consolation for a half in which they were outclassed.
The Vodacom Bulls may have lost some momentum late in the first half, but they were back in control five minutes after the restart when Ruan Nortje (lock) - who was named Man of the Match - scored their sixth try from an intercept in their own half, and raced away from the cover defence.
Seven minutes later, Grobbelaar got his second try – a sublime team effort – from a move that again started in their own 22, with cross kicks, offloads, slick passing and determined running all part of the package.
Coetzee scored his second in the 72nd minute from a rolling maul and Robert Hunt (replacement prop) also crossed the whitewash shortly before the end, before experienced Wales prop Rob Evans got a consolation try after the hooter had sounded for Scarlets.
Vodacom Bulls 57 (31) – Tries: Canan Moodie, Marcell Coetzee (2), Cyle Brink, Johan Grobbelaar (2), Elrigh Louw, Ruan Nortje, Robert Hunt. Conversions: Chris Smith (5), Morne Steyn.
Scarlets 12 (7) – Tries: Sione Kalamafoni, Rob Evans. Conversion: Rhys Patchell.