Is mac OS 10.6.8 compatible with MacBook Pro 15 late 2011?

No, you cannot install an earlier version of the OS than the one that was preinstalled.

It is easy to confirm this: put the OS 10.6 DVD in the MBP and try to install it in the usual way by holding the C key down when you restart the computer. There is no risk in trying this.

You cannot install 10.6.8 on a Mac that came with 10.7.

To run Snow Leopard on an external HD you need to install Snow Leopard Server, not the plain SL.

The REAL answer is YES if you have 10.6.7 or 10.6.8 as a clone on an external disk you can boot your model Mac from it.

The Late 2011 models are so close to the Early 2011 models, in hardware specs and drivers needed for the hardware, that Snow Leopard will run on it without problems.

And you could even Clone your external drive with 10.6.8 to a separate partition on the internal drive and it will work.

MacOS 10.6.8 runs without problems on my Macbook Pro late 2011. I created it on a hackintosh with an original Snow Leopard DVD and then when that runs I put my Macbook Pro late 2011 in Target disk mode and used CCC to clone the OS to my MacBook Pro. There I created a tiny HD first with Disk Utility. Few people seems to understand that you can use Disk Utility to create a new HD on an existing one. No data will be erased.

I believe there are more way to install 10.6.8 but this was my way. It is true that you cannot install lower version numbers because of the Sandy i7 Proc. But 10.6.8 runs fine. Good luck!

Forgot to say you need to update the SL to 10.6.8 before you clone to MBP! Otherwise it won't run! Sorry.

You can update on an original older Mac or use a hackintosh for this which is easy to build from a existing PC in most cases when using Intel's hardware or Gigabyte MB. You can visit tonymacx site for that. Thanks to Apple who made this all possible!

Running OS X 10.6.8 Snow Leopard on a MacBook Pro Late 2011 is possible. I have it installed on my 13" Late 2011 MacBook Pro, that hardware between the Early 2011 (Comes with SL) and the Late 2011 (Comes with Lion) are basically identical in terms of hardware and drivers. I pretty much installed Snow Leopard on an older Mac and cloned the system to an external drive. Plugged it into my MacBook Pro, and it runs flawlessly! After that, I cloned the files from the external drive onto a partition on my internal HDD, now I can run Snow Leopard as if the machine came with it.