Teacher educators have a challenging task of designing opportunities for preservice teachers (PSTs) to learn ambitious science teaching (AST). However, with limited time in methods courses and the complexities of AST, opportunities for PSTs to "try out" ambitious instruction are difficult to construct and analyze. To address this problem, we describe our enactment of a type of extended pedagogical rehearsal that we call "macroteaching" in a secondary science methods course. Framed as a design experiment, we codeveloped macroteaching with the PSTs during methods class, examining how we all learned about AST given the extended learning opportunity. The results of this study, including that PSTs are not afraid of the uncertainty about what students might say and do, suggest that extended rehearsals of AST provide PSTs and the course instructors with opportunities to advance their teaching and vision of the profession in a methods class.