Organic Group visible only by authenticated user
I used the Content Access module to deny access to anonymous user. 

In your Organic Group content type admin interface (admin/structure/types/manage/committee) a new ACCESS CONTROL tab appears. Unckeck anonymous user for the view View any committee content.

If authenticated user is check it will over-right Organic Group settings (ie. the Private / Public will have no effect and the content will be accessible to all authenticated user).

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