For an organization to realize the intended benefits of an enternprise resource planning (ERP) investment, it must integrate both technical expertise and functional area knowledge, and it must have continuing support after implementation. The study aims to expand understanding of how organizations ensure the necessary support from functional experts during and after ERP installations. In particular, the study aims to address the question of the type of horizontal support mechanism chosen for this support and how managers make these choices. The study is a replicated case study based on interviews with project leaders in nine universities judged to have successful People Soft ERP implementations. Thematic analysis is applied to identify the factors influencing managerial choices and organizational decisions made to assure post-implementation ERP support. The findings indicate that managers of ERP implementations recognize the necessity for horizontal coordinating mechanisms both during and after implementation. The paper finds no single “best” structure in the cases, nor does it observe that the support structure decision is always based on a deliberate organizational strategy. The findings indicate that selection of post-implementation support structure is often a negotiated outcome. Ultimately, the paper finds that the outcomes were based on three factors: the situated context of the original implementation project goals; the nature of early commitments made to functional subject matter experts and their departments; and the initial project structure used during the implementation phase. This research fills a gap in research on ERP support structures by examining how localized organizations assure the necessary support from subject matter experts, commencing with project inception and continuing through post-implementation. The results contribute to theory by illustrating the value of a process-based approach to understanding the factors that affect the choice of support structures. The findings contribute to practice by highlighting how early management decisions and the methods executives chose to assure commitments from key stakeholders can restrict the range of options for post-implementation organizational structures. © 2012, Emerald Group Publishing Limited.