Focusing on gas, this article explores the role of the European Commission in the process of European Union energy security policy development, and the extent to which the policy area is becoming increasingly supranational. Situating the article within the literature on agenda-setting and framing, it is argued that a policy window was opened as a result of: enlargement to include more energy import dependent states, a trend of increasing energy imports and prices, and gas supply disruptions. From the mid-2000s, the Commission contributed to a shift in political norms, successfully framing import dependency as a problem requiring an EU-level solution, based on the institution's pre-existing preferences for a diversified energy supply and internal energy market. Whilst Member States retain significant sovereignty, the Commission has achieved since 2006 creeping competencies in the internal, and to a lesser extent external, dimensions of EU energy policy. (C) 2012 Elsevier Ltd. All rights reserved.