A method and apparatus for determining a list of members for a Group Push to Talk Session in a communications network. A Search Proxy function receives, from a requesting network node, a search request message. The search request message comprises at least one of an instruction to limit the maximum time for a search operation to take, an instruction to send search results in segmented blocks, an instruction to send search results in a predetermined format; and an instruction to perform a search according to a predetermined pattern. The Search Proxy function then performs a search for members with which to populate the list and sends the search results to a receiving node. In most cases, the receiving node is the requesting node.