Recent years have seen a proliferation of state supports to increase agriculture and rural economic development through co‐operative ventures. Implicit or explicit in these activities is the mobilisation of social capital to achieve economic aims. To date, few studies have addressed the long term evolution of social capital‐based relationships. In this article, we assess the evolving role of social capital in an agricultural co‐operative, using the development of machinery rings in Scotland as a case‐study. Drawing on Bourdieu's conceptualisation of capital exchange, we explore the establishment, formalisation, and commoditisation of different capitals embedded in the rings. Findings demonstrate that a range of capital types was important at each stage of machinery ring development, enabling them to evolve in relation to the changes affecting the agriculture industry in Scotland. Early adoption of advanced information technologies enabled the mobilisation of network resources and successful service provision across increasing geographical scales. Through formalisation, the rings became sources of human, social, and economic capitals – access to which could be purchased by new ring members. This formalisation process ultimately led to the establishment of the rings as economically viable businesses, but also a shift in identity from farmer collaboration to commercial service provision.