Buyer-supplier relationships in purchasing and supply chain management practice are instrumental and often “messy”. Indeed, the buyer and the supplier generally interact while pursuing their own interest, which are often subject to change over time. The action research method can help address the complexity of buyer-supplier relationships, generating important theoretical insights and relevant managerial implications. First, action research helps the researcher to better understand the problem by integrating diverse perspectives. Second, it allows the researcher to influence the buyer-supplier relationship directly, providing mutually beneficial solutions. This study proposes action research as a suitable interactive method that could complement other methodologies in the field of purchasing and supply chain management, as well as in other fields. An expanded action research framework – the “action research cycle reloaded” – is proposed and the role of the action researcher in the buyer-supplier context is discussed. The framework is applied to study the design and implementation of a supplier performance measurement system in the banking industry.