Isomorphism has been widely used to describe why trends penetrate entire organizational fields. However, research so far has neglected the temporal aspects of such diffusion processes and the organizational reasons underlying the introduction of new management tools. We argue that during reform waves, the reasons for adopting the new tools differ over time. Using comparative data from two surveys on quality management in the field of higher education and the health sector, we show that early adopters are more likely to be motivated by instrumental reasons, while late adopters will more likely be motivated by institutional reasons.