Actually, its "Oriented Strand Board", not Oriental. As in, when you look at the wood chips pressed, glued, and oven baked together, they have directionality. Its stronger than Plywood in sheer, otherwise very similar characteristics
Some claim its superior to plywood in exterior/high moisture applications due to the use of heat-cured waterproof adhesives in the manufacture, but its been my consistent experience that the wood usually fails, not the glue - in either product.
As alternative to a saber saw or a jig saw, you could also use a rotary tool with a circle jig.

(Essentially a flat stick to which the rotary tool is attached, secured at the correct radius by way of nail or screw to the object being cut)