Assigning all users to a role with a mass change

Hi, I have a membership site with nearly 8000 users that i want to assign to a role using the Membership plugin. Is there an easy way to assign everyone to a level without having to trawl through page after page of members adding them all?

When you are in a post type page in the admin you can normally change the screen options so that you can view a different number of items. Is this possible with the members as this would make it a lot easier?

Thanks

Matt