This paper addresses the collaborative processes flexibility issue, which is an important issue in Business Process (BP) Management. Indeed, the strong competition in which organizations are involved lead them to frequently change and adapt their collaborative processes to face new client requirements or to benefit from new collaboration opportunities. More precisely, this paper proposes to adopt a version-based approach to support the modelling of flexible collaborative processes. First it introduces the VBP2M meta-model (Version of BP meta-model) supporting the modelling of flexible internal (i.e., intra-organizational) processes, and then explains how to extend it to define the VCP2M meta-model (Version of Collaborative Processes meta-model) to design flexible collaborative processes, which correspond to processes crossing the boundaries of companies. A specific case study illustrates the modelling of collaborative process versions as instances of VCP2M.