How an organization may achieve ERP (enterprise resource planning) assimilation effectively remains a problem. To address this, this paper develops a model based on institutional context, technology adaptation theory, and theory of technology assimilation to test the main effect of management support's metastructuration actions on ERP assimilation, and examines how ERP technology adaptation moderates the relationship between management support's metastructuration actions and ERP assimilation. The resulting contingent model is tested using a questionnaire survey of 201 Taiwan manufacturing firms. Most of our hypotheses in the model are supported. Implications for both theory and practice are provided.