I've set up a Beehive Online workspace but am unable to add participants outside of my cost center.
I loigged a ticket with the help desk but they referred me to this forum.
Did you add those users to the Beehive Online group? You cannot add users who are not part of your group to the Beehive Online workspace directly. If the user if not a member of the group you are in, you will not be able to see them in the New>Participant screens. The fact they are an oracle employee is irrelevant.
Please refer to the FAQ's and Getting started section in BOL