@astangelo,
I just designed a new responsive email template for my employer, and came across the EXACT same issue with Outlook for Mac.
After googling a bit, I found out that oddly enough (and in really great news), Outlook 2011 for Mac uses the Webkit rendering engine, not Microsoft Word.
So, you cannot target it using conditional comments that you usually would for other PC-based versions of Outlook.
All you need to do is add an @media query in your head styles and specify a max-width using (preferably) a table["attribute"="property"] selector.
I just did this and tested it and it finally fixed my issue.
Make sure you use Premailer's CSS inlining tool, and 'Check' the 'Don't remove or from the head', otherwise your @media query won't come through and the trick won't work.
I hope this helps!
Sincerely, Robert