Actually anyone with a Mac running 10.10.5 or 10.11 and an A7Rii could answer this for me I think.
I can see the COMPRESSED raws just fine and preview them with Preview.
But the UNCOMPRESSED raws that were added in a firmware update I can't see with OSX. It just displays a black frame once it renders its own preview rather than using the jpeg embedded in the raw.
C1Pro sees both fine (but also threw a fit when first presented with the uncompressed raws, until Phase One updated it).
What I'm asking is can OSX see the uncompressed raws in 10.10.5 ? Sorry, didn't think clearly enough about the question I was asking!
It really isn't an issue so much of which version of OS X you are using, as long as it is still current enough to utilize Apple's Camera RAW updates to CoreImage. Unlike C1Pro and Lightroom ... Aperture, iPhoto, Preview and the new Photos app, RAW rendering is handled at the system level, not the individual app level.
Make sure you have the most recent update to Apple Camera RAW (simply check for updates via the Mac App Store app.)
If this update to the A7Rii is a recent one, it likely hasn't been included in any recent OS X updates. You may have to wait for that update. Unfortunately, these Camera RAW updates are not on a specific timetable but Apple responds rather efficiently.