Thanks. I have one similar to that, and it's showing good ground on what the previous owner did.

I knew I could get good ground through the green wire on the MC cable, I just didn't know if there were any issues with changing the "medium" (for lack of a better word) of ground on a circuit or if there was a better way.

The current outlet was grounded through the conduit, but the whip I bought was MC and that sheath shouldn't be used for ground. So it will be ground through the conduit up to the point that the homeowner stopped. I'll attach the green wire to that existing box to ground my new outlet.

So when I'm done the ground will look like:

(New Outlet) --green wire--> (Existing Outlet Box) --conduit--> ground

I was trying to figure out if it was ok to do half a circuit grounded through one type and the other half another.