Delegation in the European Union (EU) involves a series of principal-agent problems, and the various chains of delegation involve voters, parties, parliaments, governments, the European Commission and the European Parliament. While the literature has focused on how government parties attempt to monitor EU affairs through committees in national parliaments and through Council committees at the EU level, much less is known about the strategies opposition parties use to reduce informational deficits regarding European issues. This article argues that the European Parliament (EP) offers opposition parties an arena to pursue executive oversight through the use of written parliamentary questions. Using a novel dataset on parliamentary questions in the EP, this article examines why Members of the European Parliament (MEPs) ask questions of specific Commissioners. It transpires that MEPs from national opposition parties are more likely to ask questions of Commissioners. Questions provide these parties with inexpensive access to executive scrutiny. This finding has implications for the study of parliamentary delegation and party politics inside federal legislatures such as the EP.