In this article we examine methodological and conceptual issues that emerge when researchers measure the enacted curriculum in schools. After outlining key theoretical considerations that guide measurement of this construct and alternative strategies for collecting and analyzing data on it, we illustrate one approach to gathering and analyzing data on the enacted curriculum. Using log data on the reading/language arts instruction of more than 150 third‐grade teachers in 53 high‐poverty elementary schools participating in the Study of Instructional Improvement, we estimated several hierarchical linear models and found that the curricular content of literacy instruction (a) varied widely from day to day, (b) did not vary much among students in the same classroom, but (c) did vary greatly across classrooms, largely as the result of teachers’ participation in 1 of the 3 instructional improvement interventions (Accelerated Schools, America’s Choice, and Success for All) under study. The implications of these findings for future research on the enacted curriculum are discussed.