In order to improve instruction, teachers need to make sense of and evaluate the critical events that have the potential to strengthen the understanding of students' mathematical thinking. Mathematics instruction has shifted toward inquiry teaching which leaves many teachers attempting to change their practices accordingly. While there are documents that help mathematics teachers understand inquiry practices, there is little guidance for teachers who teach in classroom settings in which students with special needs are included. Since mathematical reasoning and conceptual understanding have become as important to teach as procedures, it is imperative that co-teachers draw on each other's knowledge to incorporate inquiry co-teaching practices. A design-based research project was conducted to explore the co-teaching practices in an inquiry mathematics classroom setting. We document co-teaching practices that are effective for planning and implementing inquiry mathematics lessons.