Griquas started at a ferocious pace and put together some useful phases of play, but lacked the clinical touch deep in the WP half.
WP were on the back in the opening minutes, but regained composure to show their class late in the contest.
Griquas maintained their attacking play and drew first blood after lock Ligtoring Landman dove over in the corner.
The forward rounded-off after some good interplay between the pack and backs.
Fullback Francois Brummer failed to convert Landman's opener, but it wasn't long before Griquas again caught WP's defence napping, as winger Wilmaure Louw rounded of in the corner.
Brummer was on target with his second attempt to give the Kimberley outfit the early advantage.
The visitors had their first real chance to get on the board when flyhalf Demitri Catrakilis took a penalty shot at goal, but his attempt in a swirling wind went wide.
WP finally scored after Griquas were beaten in defence through a sustained period of attack.
Wing Ederies Arendse ran 25 metres for the highlight of a very poor first half by the visitors, the score 12-7 at the break.
Brummer kicked a penalty early in the second period, but Province launched a come-back through centre JP du Plessis, who scored after a quick tap to get his team within three points of Griquas.
Griquas were forced to defend their lead and made several crucial tackles, but their tired bodies showed in the last 15 minutes as WP drove them back into their own area.
Province used it to their advantage and prop Steven Kitshoff dove over under the posts after some slack defence by the hosts.
Griquas
tried to salvage a bonus point and succeeded when lock Jaco Nepgen
burst over, but with two minutes on the clock and the conversion to
come, the hosts narrowly missed out to their Western Cape counterparts.