The key challenge for an organisation implementing and using an ERP system is to understand and enact new business processes inscribed in ERP; and thus, undergo a profound organisational change. As continuation of a previous study, this paper provides a summary of the results of the previous study showing as a background to the second part of the current study. In the second part, the authors provide details of a proposed research methodology for the longitudinal case study. Results from the previous study show frustration and struggle of the staff and management of the case study organisation about the implementation of the SAP on the go-live day which lasted over five months. The focus of the current study is to provide detailed description of a proposed research methodology that facilitates further understanding of the ERP post-implementation phase using the organisational learning, enactment and the Community of Practice as the theoretical lens. The execution of the proposed research methodology is the subject of the authors’ future study.