Many major urban districts have committed large investments to school-based professional development anchored in the work of literacy coaches. At base is a shared belief that instructional coaches are key levers for improvement. Yet, clinical accounts of the role of an instructional coach suggest that this is a complex practice to implement well. This article seeks to add to this literature through a theory-based quantitative investigation of literacy coaching as enacted in a mature school reform initiative. We examine teachers' actual exposure to Literacy Collaborative coaching and analyze the variability in this exposure both within and between schools. We theorize about the factors at both the individual and school organizational levels that might contribute to this observed variability and test the predictive power of these ideas using data from a longitudinal study of 250 teachers in 17 schools. (Contains 2 figures, 4 tables, and 13 notes.)