This study investigated the influence of direct modeling of a supplemental classroom program on the early literacy beliefs and practices of Head Start teachers. Developed by speech language pathologists (SLPs), Systematic and Engaging Early Literacy Instruction (SEEL) was not undertaken with an explicit professional development goal. However, the potential significance regarding professional development became apparent as teachers collaborated with literacy specialists (SLPs) who conducted supplemental literacy activities in the classrooms. Data were collected by interviewing teachers at the end of each year of participation and again two years later. Transcripts were reviewed for relevant themes. Results demonstrate that teachers' early literacy understanding and practices were influenced by exposure to SEEL as teachers expressed an understanding of key strategies used by the program and made observations of student performance. Implications are discussed regarding the use of supplemental classroom intervention programs as methods of professional development for classroom teachers.