This study investigates the influence of a school's pre-existing social resources on the implementation of a comprehensive literacy-coaching program (Content-Focused Coaching [CFC]). Elementary schools were randomly assigned to receive a CFC-trained coach (n = 15 schools) or to continue with the literacy coaching resources that are standard for the district (n = 14 schools). Ninety-six fourth-and fifth-grade teachers participated in the study (n = 63 CFC and n = 33 comparison). Survey results indicate that teachers in the CFC schools participated more frequently in the coaching activities that emphasized planning and reflecting on instruction, enacting instruction, and building knowledge of the theories underlying effective reading comprehension instruction compared to teachers in the comparison schools. After 1 year, teachers strongly believed that CFC coaching helped improve their instructional practice. Principal leadership was the key resource supporting implementation of the program positively predicting greater teacher participation in coaching activities and perceived usefulness of these activities along with coaches' training in the CFC program and less experienced teachers. Unexpectedly, a school's pre-existing culture of teacher collaboration negatively predicted teachers' coaching experiences. CFC coach interviews contribute to understanding the interactions of social resources within schools that facilitated or hindered program implementation. Implications for the design and implementation of effective instructional coaching policies in districts are discussed. (Contains 2 notes.)