Mathematics content courses for prospective elementary teachers (PTs) should provide them with opportunities to deepen their understanding of and develop productive dispositions toward mathematics. Supporting mathematics teacher educators (MTEs) to learn how to develop practices that create rich learning opportunities for novice teachers comprises a challenge for our field. This analysis examines an unconventional professional learning experience for MTEs: viewing video of experienced teacher educators enacting the "same lessons" that they would enact with their own PTs. We examined how viewing videos embedded in a larger set of supports developed by the "Elementary Mathematics Project" (EMP) impacted MTEs' actions when planning or enacting the lessons. EMP also includes high-quality curriculum materials to use with PTs and instructional guides to support their enactment. Twelve MTEs were interviewed about their experience viewing video clips to help them to engage in preparation (Mason, 2011) as they prepared to enact EMP lessons. MTEs' noticings included how prospective teachers engage with the mathematics and one another and how the expert MTEs supported prospective teacher interactions and aspects of the classroom environment. MTEs connected the actions they identified to broader principles of teaching, offering a rationale for each and hypothesizing how it impacted the instruction. Importantly, through watching video, MTEs generated conceptual resources (e.g., identifying questions asked in the video that they wanted to try out), which they reported allowed them to respond to prospective teachers in the moment when teaching. Implications for using video to support MTE development are discussed.