Kamo came roaring out of the blocks as a beautiful offload from prop Dave Fotu led to first-five Ethan Bracey crossing over in the corner.
OBM struck back with an offload of their own as first-five Jayd Kapa laid one on for second-five Mychal Seymour.
After OBM kicked a penalty, Kamo took the lead as hooker Kahu Boyd scored after a series of breaks.
Kamo extended their lead before the break through a penalty from centre Jayden Gravatt and a five-pointer from impressive blindside flanker Thomas Barlow.
This gave them a handy 20-10 lead going into the break.
OBM were still in the contest at this point but with the introduction of Kamo's bench, it all fell apart for the defending champions very quickly.
Kamo immediately put pressure on the OBM pack and forced a lineout error inside their 22, giving Barlow an opening to cross for his second try.
The introduction of halfback/first-five combination Kurt Davies and Tom Herman added another element to Kamo's already impressive attack.
Davies picked off a nifty blindside try after brushing off a couple of tackles, which Herman duly converted from the sideline.
Jayden Leaupepe scored shortly afterwards, giving Herman another difficult sideline conversion. Again, he calmly slotted it with no fuss.
The likes of man-of-the-match second-five Adam Shepherd and fullback Kalib MacDonald were always threatening for Kamo.
Meanwhile OBM lock Andrew Blomfield and flanker Kirk Bruce made their presence known in the pack.
McDonald continued Kamo's dominance with a try of his own before putting a perfectly placed chip kick on for wing James Dempster to pick up and score.
OBM prop Shaun Damora picked up a consolation try at the end but after Barlow completed his hattrick once the siren had sounded, the result was emphatic.
