Large-scale educational studies frequently require accurate descriptions of classroom practices to judge implementation and impact. However, it can be difficult to obtain these descriptions in a timely, efficient manner. To address this problem, the authors developed a vignette-based measure of one aspect of mathematics instructional practice, reform-oriented instruction. Teachers read contextualized descriptions of teaching practices that varied in terms of reform-oriented instruction, and rated the degree to which the options corresponded to their own likely behaviors. Responses from 80 fourth-grade teachers yielded fairly consistent responses across two parallel vignettes and moderate correlations with other scales of reform-oriented instruction derived from classroom observations, surveys, and logs. The results suggested that the vignettes measure important aspects of reform-oriented instruction that are not captured by other measurement methods. Based on this work, it appears that vignettes can be a useful tool for research on instructional practice, but cognitive interviews with participating teachers provided insight into possible improvements to the items.