Purpose– The purpose of this paper is to address global sourcing organisational design through the following research questions: how do the roles performed by International Purchasing Offices (IPOs) change over time?; what are the resources/capabilities required by an IPO for an effective performance and how do they change over time?; and what are the contingent factors affecting such changes?Design/methodology/approach– The authors employed an exploratory multiple case study approach and analysed 14 Western IPOs located in China for a period between 2007 and 2012. The data were primarily collected through 34 direct, semi-structured interviews of IPO heads and sourcing managers or senior buyers.Findings– The authors identify and discuss the importance of ten roles played by IPOs and 12 required resources/capabilities. Furthermore, considering the changes that occurred to these IPOs over a five-year period (2007-2012), the authors observe three distinct evolutionary behaviours (i.e. “overall development”, “selective development”, and “stable configuration”) and highlight three contingent factors that jointly affect these behaviours (i.e. the architectural and technological complexity of the sourced items, annual volume sourced abroad, and experience in the foreign context).Originality/value– This paper contributes to the resource-based view of the firm in a global sourcing context by highlighting the resources/capabilities required by IPOs and discussing their characteristics. Furthermore, it proposes a typology of IPO micro-organisational evolutionary behaviours. Finally, it applies contingency theory and identifies three factors that might affect the evolutionary behaviours.