The reasons that constructivist approaches to the EU have often refrained from asking questions on institutional conflict and rapidly unfolding institutional change are not self-evident. To explore the potential of these approaches to deal with these questions, a more in-depth discussion is needed. It will clarify why the division of work between rationalist and constructivist approaches in EU studies is largely unfounded. It furthermore points to how constructivist conceptualizations of how institutions and agents interact over time can help supply vital clues regarding how new preferences arise, how cooperation breaks down and how institutional boundaries are redrawn.