A one-size-fits-all model of instruction cannot provide equitable access to education for all students. Research demonstrates that thoughtfully changing instruction to support student learning during a lesson, known as adaptive teaching, is an important component of effective literacy instruction. To understand this dynamic dimension of effective instruction, our research team created an observation protocol to capture different adaptations made by literacy teachers, as described in the extant literature. This manuscript focuses on the development and refinement of the Adaptive Teaching Observation Protocol (ATOP), an instrument designed to enhance research and professional development.