In this paper, we offer a framework for "teacher monitoring routines"--a consequential yet understudied aspect of instruction when teachers oversee students' working together. Using a comparative case study design, we examine eight lessons of experienced secondary mathematics teachers, identifying common interactional routines that they take up with variation. We present a framework that illuminates the common moves teachers make while monitoring, including how they "initiate" conversations with students, their forms of conversational "entry," the "focus" of their interactions, when and how they "exit" the interaction as well as the conversation's overall "participation pattern." We illustrate the framework through our focal cases, highlighting the instructional issues the different enactments engage. By breaking down the complex work of groupwork monitoring, this study informs both researchers and teachers in understanding the teachers' role in supporting students' collaborative mathematical sensemaking.