Research Findings: This qualitative study examined how Head Start teachers thought about children's early literacy and how they enacted their thinking in a year-long curriculum reform effort. Data collected included interviews, observations, questionnaires, concept maps, and teachers' reflections on implementation. The results indicated that as teachers implemented the new curriculum, a number of factors influenced their instructional practice. Four cross-case themes emerged: Volunteering to Change, Teachers' Perspectives About Early Literacy, The Relationships Within Teaching Teams, and The Head Start Context. Practice or Policy: Findings are discussed as they relate to improving early literacy instruction through the use of curriculum. Implications for practitioners and teacher educators are outlined, including the importance of addressing gaps in teacher knowledge, facilitating skill development, and influencing teachers' motivation to engage in change. Equally important to consider are factors that may influence a teacher's readiness to change his or her practice and emphasizing the need for supportive environments as teachers work to enhance children's early literacy development. (author abstract)