Globally, schooling continues to be a precarious space for gender and sexuality diverse (GSD) youth, where students are more likely to experience transphobic and homophobic violence at school than at home or in the general community. While there have been moves to provide learning about GSD in preservice teacher education, limited attention has been given to how postgraduate programs might better equip inservice teachers to support GSD students. In this paper, we argue that Master of Education (MEd) degrees, that serve teachers and school leaders, represent a space for transforming teacher attitudes and practice. Our research in a large, metropolitan university in Australia explored the use of reflective online writing in an MEd by coursework critical sociological studies course. Threshold concepts and liminality were used as a theoretical framework to explore how nineteen inservice teachers engaged with content on GSD and education. Our research findings suggest that while some students may feel discomfort as their existing knowledge is challenged, providing a safe space for critical reading/thinking and for connecting theory with personal and professional experiences enables students to move through phases of liminality. This opens up opportunities for teachers and leaders to challenge cis-heteronormative attitudes, practices and policies in education.