New teacher evaluation reform efforts in the United States hold principals accountable for improving teaching and learning. Yet little is known about how effective principals are at these instructional leadership tasks or how principals experience and adapt to the demands of teacher evaluation reform over time. In the current study, principals (n = 78) in a Race to the Top state--Illinois--completed an online survey after the first and second year of implementation of a new teacher evaluation system. Principals felt significantly more confident in how to conduct formal classroom observations, placed more value on student achievement data, and placed less value on additional artifacts over time. Individual- and school-level factors were related to some aspects of principals' adaptations over time. Implications are discussed.