Examining repeated classroom encounters over time provides a comprehensive picture of activities. Studies of instructional practices in classrooms have traditionally relied on two methods: classroom observations, which are expensive, and surveys, which are limited in scope and accuracy. Teacher logs provide a "real-time" method for collecting data on classroom practices by giving teachers a tool to document and reflect about specific lessons and the impact they may have had on their students. Logs can collect data for review by teachers, their colleagues, administrators, and researchers. These self-reported data, collected online repeatedly over a specified period of time, present a series of snapshots that capture ongoing classroom practices and lesson strategies. In this article, we describe the use of teacher logs to understand classroom practices by highlighting the kinds of activities teachers emphasized and their perceptions of effectiveness. In a National Science Foundation-funded evaluation of a high school reform program, we used online teacher logs to understand the education delivery in Science, Technology, Engineering, and Mathematics (STEM) subjects in redesigned North Carolina high schools. We find that teacher logs are an appropriate, efficient, and useful tool for documenting practice. Teachers can use log data to reflect on practice, determine areas of strength and challenge, and set goals for personal improvement. Administrators can use logs to support teachers in examining practice and setting goals.