Creating play environments for children usually requires groups of adults working together. An extensive scientific literature describes how groups function to achieve shared goals in general terms, and groups attempting to empower play may find this literature useful. Design principles for managing natural resources, identified by Elinor Ostrom and for which she received the Nobel Prize in 2009, provide an exceptionally practical guide for all groups attempting to achieve common goals. In this article, the authors discuss the related scientific literature and connect it to the experience of two national organizations creating outdoor environments for play--KaBOOM! and City Repair.