Purpose: The purpose of this study was to examine how preservice teachers (PSTs) developed their adaptive competence in lesson planning through repeated rehearsals and reflections in an online learning environment. Methods: A case study design utilizing descriptive analysis was used to analyze data collected from a series of lesson plan iterations made by nine PSTs in a physical education teacher education program. All participants attended one online introductory methods course, which consisted of a synchronous lecture and laboratory components to learn fundamental instruction and management skills in teaching physical education. Findings: PSTs made positive adaptations in five core practices in their lesson plan iterations. However, the frequency of adaptations in each core practice varied in different lesson components. The findings suggest that the complexity of content being taught and opportunities embedded in each lesson component may influence how adaptations were made in lesson plans. Conclusions: Repeated rehearsals and reflections can facilitate PSTs' development of adaptations in lesson planning in an online environment. However, learning environments may prevent PSTs from adapting certain core practices.