Theoretical perspectives on spelling characterize development as a progression through qualitatively different phases or as a process of more or less continuous growth. This study investigated the potential utility of a different perspective, the overlapping-wave model, for characterizing spelling development (Rittle-Johnson & Siegler, 1999). In addition, the study examined the relationship between students' developing use of spelling strategies and their spelling errors. We employed a microgenetic, mixed-design approach with multiple forms of data for triangulation. We administered six spelling inventories to 31 first-grade students individually over a period of five months in a trial-by-trial investigation. Our findings showed evidence of the three requirements for the overlapping-wave model: (1) variability, (2) gradual change, and (3) adaptive choice. Our findings also suggested a reciprocal relationship between spelling strategy use and developing orthographic knowledge. Additionally, our data showed evidence of a Matthew effect. The results of this study extend prior research by demonstrating a more complex view of spelling development and the need for additional studies employing a fine-grained analysis of developmental spelling. (Contains 4 figures and 6 tables.)