Absorptive capacity (AC) has been identified as the ability of firms to acquire, assimilate, and apply external knowledge, and thus as a precondition for learning from external knowledge. However, extant literature has focused on AC as (1) a static and (2) a firm-centred concept. In particular, there is little conceptual framing and empirical evidence of how AC develops over time and across boundaries. Taking R&D consortia as the unit of analysis and based on insights from three in-depth case studies of collaborative R&D, our contribution is a framework for AC development over time and across inter-organizational, intraorganizational, and practice boundaries at different stages of collaboration in R&D consortia. Using this framework, we identify a set of mechanisms which enable the development of AC and we discuss the preconditions for these mechanisms. For R&D managers, our research implies that in order to enhance effectiveness of knowledge transfer and learning in R&D consortia they need to develop a strategy that (1) supports learning and AC development throughout the whole cycle of the collaboration, not only by focusing on intra-firm capabilities, but in particular by providing flexible interfaces for overcoming a variety of interaction and learning boundaries between heterogeneous R&D partners, and (2) enables the integration of created and acquired knowledge within the organization once the collaboration is over.