RISE AB Consultant Group communication over the Constrained Application Protocol (CoAP) can be secured by means of Group Object Security for Constrained RESTful Environments (Group OSCORE). At deployment time, devices may not know the exact OSCORE groups to join, the respective Group Manager, or other information required to perform the joining process. This document describes how a CoAP endpoint can use descriptions and links of resources registered at the CoRE Resource Directory to discover OSCORE groups and to acquire information for joining them through the respective Group Manager. A given OSCORE group may protect multiple application groups, which are separately announced in the Resource Directory as sets of endpoints sharing a pool of resources. This approach is consistent with, but not limited to, the joining of OSCORE groups based on the ACE framework for Authentication and Authorization in constrained environments.