This study adds to a vibrant scholarly literature on the consequences of differentiated European integration by demonstrating mechanisms of European integration without membership. This study suggests how European integration also manifests itself beyond the formal members of the Union and in effect render the EU membership vs. non-membership dichotomy increasingly blurred. It does so by presenting a novel longitudinal data set that probes how essential parameters of domestic public governance in a non-EU member state are profoundly influenced by the EU. The data consists of a comprehensive large-N (N = 3562) questionnaire study among Norwegian central government officials at three points of time: 1996, 2006 and 2016. The data suggests that even in formally non-EU member states, government officials are tightly interwoven and influenced by EU institutions. The data shows, over time, (i) that ministerial officials have become tightly integrated into and affected by the EU’s multi-level administrative system, and (ii) (administrative) integration beyond membership is promoted and nudged by ‘favorable’ organizational conditions at the domestic level of government. Thus, however ‘hard’ Brexit is eventually going to be, the United Kingdom is likely to experience fairly similar mechanisms, accompanying strong administratively tied to the EU - even as an EU-‘outsider’.