In 1901 Muzaffar al-Din, the Shah of Persia, granted William Knox D’Arcy a vast concession, which enabled the British billionaire to “search for, obtain, exploit, develop” natural gas, petroleum, asphalt and other mineral products across most the territory of the Persian Empire. After searching unsuccessfully for oil at the border with Iraq, the engineers of d’Arcy’s company moved men and machines to the territory of Persia’s largest nomadic tribal group, the Bakhtiari, in the Zagros mountains. From 1905 and until 1914, the Concession Syndicate, a forerunner of British Petroleum, would go on to obtain land from the Bakhtiari and build up infrastructure for oil exploration and extraction. In this way, over a compressed period of time, two different and ‘incommensurable’ forms of territorialization and of social ecology came to compete with one another in the Zagros mountains: on the one hand the territory of the Bakhtiari tribe, and on the other hand the Company’s territory. Meanwhile, over these decades and subsequently, the Bakhtiari were also drawn upon to provide a labour force for the Company’s needs: by employing Bakhtiari men as workers on oil extraction and production sites, this led to a process of transformation in the tribe. Two projects were therefore connected in British oil imperialism: the creation of a new commodity frontier was intertwined with a project to transform the Bakhtiari, based on racialized capitalist and colonial ideas about governance and production. The extensive historiography on British oil imperialism in the Middle East has paid relatively scant attention to indigenous actors; and only limited work has been done on the environmental and social dimensions of this key moment within a larger British imperial project geared around the mastery of natural resources. Using a historical anthropology approach, this paper sheds light on the multiple ways in which the Bakhtiari reacted to the environmental and social changes brought by oil. It contends that archival records which survive for this conjuncture do not simply track the “forms of resistance” of the Bakhtiari tribe to the capitalist endeavours of the British oil companies. Rather, what we witness in the sources — for the most part, Company and official records requiring reading against the grain — is more a process of reconfiguration of the Bakhtiari tribe. After a moment of inter-tribal tension and violence, the tribe adapted to the changes brought by oil and the material structures built by the British oil companies.