A growing body of scholarship in teacher education has explored the historical, systemic, interactional, and individual factors that create possibilities and challenges in White teachers' reconceptualization of their racial identity and of the purpose and nature of their work in a racialized society. However, there has been little attention to programs of teacher education as critical mediators of such learning and change. Through an analysis of in-depth interviews with four prospective White teachers in the United States, we develop a framework of White teachers' racial identities as situated within racial ideologies and mediated by the context of teacher education programs. The framework helps elucidate how teachers' racial identities are instantiated through interactions and available identities in a program space, which are in turn shaped both by ideology and program structure and culture. The framework and findings urge an insertion of our own agency, as teacher educators, into the analyses of White prospective teachers' learning and change, by highlighting our role as individuals who co-construct the programmatic structure and culture that partially instantiates these teachers' racial identities.