European Commission officials are usually thought to prefer more to less supranational authority. A large body of work assumes that they maximize the power of their organization. This study suspends a priori preference attribution and empirically investigates variation in support for supranational authority over five policy areas. The analysis uses Kassim et al.'s survey data from 2008 (N = 1,901). The first finding in this article is that Commission officials do not systematically prefer more supranational decision‐making. Following the logic of fiscal federalism, they support changes in EU policy scope to the extent that this would improve public good provision. The second finding, taking a political psychology perspective, is that individual calculations of efficiency are mediated by ideological beliefs. Because issues are complex and information is costly, Commission officials rely on heuristics to assess what the European Union should do. They are biased information‐processors.