In Kenya, the pastoral Maasai’s districts have been the vanguard in rangeland tenure transitions and experimentation as pastoralists’ territory gave way to communal group ranches and to individual land holdings under diverse land-use activities. The tenure transformations have been accompanied by institutional and socio-economic changes that have had bearings on local communities’ capacities for collective action, pastoral livelihoods, and environmental sustainability. While studies of the tenure transitions have focused more on the effects of sub-division and privatization, less consideration has been given to resilient, functional, communal resource institutions in the region. This paper considers the case of Olkiramatian group ranch, which has appropriated the “modern” group ranch framework as an institutional base for the local collective management of communal resources and socio-economic organization. While the framework provides the organizational structure for local resource institutions, shared local knowledge and social values, common interests, and customary relations provide the cement that makes them functional. Moreover, the rare combination of an extreme arid ecology, perennial rivers, potential for tourism-conservation, and long standing interaction between pastoralism and cultivation, inherently creates opportunities for economic diversification and need for institutionalized resource management. Recent pressure for land individuation, on the other hand, presents opportunity for greater tenure security but threatens the communal collective whole.