Forms Authentication and AD Group Membership

Okay, this is seriously frustrating.  I have search 100's of posts and no one seem to be trying what I am attempting to do... or at least, no one has found an answer.  I am using Forms authentication against Active Directory.  While authentication works, I cannot figure out how to only grant access to users of a particular Active Directory group.  Here is what is in the web.config:

   <authentication mode="Forms">
   <forms
    name="OSAFADAuthCookie"    
    timeout="10" />
  </authentication>

 <authorization>
   <deny users="*" />
   <allow rolse="saf_users" />
  </authorization>

  <membership defaultProvider="MyADMembershipProvider">
& ...