Elementary teacher education involves learning to teach science. Even in elementary school, teaching science is demanding work--teachers must orchestrate a complex set of teaching practices to support students' science learning. This dissertation examines the application of Grossman and colleagues' (2009) cross-professional learning framework, highlighting approximations of practice in the form of simulated teaching experiences, to support prospective elementary teachers in learning to teach science. Specifically, approximations of practice focused on investigation lessons or lesson portions were designed and incorporated into an undergraduate elementary science teaching methods course. Using qualitative research methods, I studied relationships between four prospective teachers' approximations of practice and their instructional approaches, ideas about, and confidence in teaching elementary science investigation lessons. I also examined prospective teachers' perceptions of the utility of approximations of practice in learning to teach elementary science. Data analyses indicate that approximations of practice served several functions. Less-authentic yet highly-supported approximations of practice provided opportunities to experience investigation lessons from teacher and student perspectives. Other approximations of practice allowed teachers to focus on parts of science lessons in elementary classrooms. Full-length science lessons in elementary classrooms provided learning opportunities aligned with authentic daily teaching responsibilities. All approximations of practice afforded opportunities to develop practice, ideas, and confidence. Prospective teachers' reflections identified benefits and constraints of learning to teach by approximating practice. Considered individually and together, approximations of practice informed and were informed by prospective teachers' evolving ideas about and confidence for teaching investigation lessons. Curriculum materials and cooperating teachers also influenced prospective teachers' instruction, ideas, and confidence. Findings support a theoretical model that positions approximations of practice, ideas about investigation lessons, confidence for science teaching, and other individually-relevant factors as highly interrelated, dynamic constructs. This dissertation study shows that approximations of practice supported prospective elementary teachers' development of instructional approaches, ideas, and confidence for teaching investigation lessons earlier than anticipated: prior to student teaching. Additionally, study findings provide insights into theory and practice of elementary science teacher education, and teacher education more broadly. Thus, this dissertation provides evidence that approximations of practice support the preparation of well-started beginning elementary science teachers. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]