create group content: how to block anonymous user but allow authenticated non-members?

[bradbulger]

Content type MyType has no Drupal role permissions granted on it at all. It's set up to be used as OG group content. The default (site-wide) OG permission "Create MyType content" is set for non-members and members.

The result is that anonymous users as well as authenticated non-members are able to create MyType nodes if they prepopulate the group audience to a valid group.

I think that this is all theoretically correct behavior. Checking different settings of the OG edit permissions seems to confirm that OG permissions override Drupal role-based permissions.

So my question is, how do I exclude anonymous while still allowing logged-in users? To OG, they're all just non-members.