Peer group supervision, particularly in multidisciplinary formats, presents a potential means of providing professional support, and specifically clinical supervision, for allied health professionals. Debate exists regarding the extent to which the activities of these groups should be formalized. Results drawn from an evaluation of a large-scale peer group supervision initiative are described. Analysis of 192 responses from professionals involved in peer groups indicates that participants in groups that used formal documentation - which adopted the tools provided in training, and particularly those that used formal evaluation of their groups - rated their groups as having better processes and greater impact. Interestingly, multidisciplinary peer groups were rated as having similar impacts, processes, and purposes as the more homogenous single-discipline groups. It is concluded that the implementation of formal arrangements enhances the processes and outcomes of peer groups implemented for professional support and clinical supervision. Multidisciplinary membership of such groups is perceived as equally beneficial as single-discipline groups.