Are you having trouble using Organic Groups Access Control with other access control modules, such as Taxonomy Access?
Normally, the Taxonomy Access module overrides the permissions set by Organic Groups Access. This means that even content which is in a private group will remain visible to users who are not members of the group if Taxonomy Access says it should.
This module makes private groups and their posts remain private. It works by giving the og_access grants a priority "boost", so it may work with other access modules besides Taxonomy Access.