I built a garage several years ago using OSB for the sheathing. I was a little short on cash at the time, so instead of putting up siding over the OSB, I stained the OSB with an oil base Olympic solid color stain. After 2 years, the OSB was showing weathering quite badly. The chips were flaking and curling as Steve said. I ended up puting vinyl siding over it.
Hope this helps,