Cluster randomized trials (CRTs), or studies in which intact groups of individuals are randomly assigned to a condition, are becoming more common in evaluation studies of educational programs. A specific type of CRT in which clusters are randomly assigned to treatment within blocks or sites, known as multisite cluster randomized trials (MSCRTs), are the most frequent in the literature. The primary question that often guides the design of MSCRTs is whether or not the program works. Hence the MSCRT is designed with the goal of being powered to detect the main effect of treatment. The purpose of this paper is to extend power calculations to moderator effects in MSCRTs. This paper extends the power calculations for MSCRTs beyond the main effect of treatment to allow researchers to also consider the power for moderator effects in the design phase of the study. A table is appended.