In recent years, commissions and reports have called for laboratory courses that engage undergraduates in authentic research experiences. We present an iterative approach for developing course-based undergraduate research experiences (CUREs) that help students learn scientific inquiry skills and foster expert-like perceptions about biology. This study involves the design, implementation, evaluation, and revision of two large introductory biology laboratory courses, where students work collaboratively on research projects developed from faculty laboratories on campus. Quantitative surveys, qualitative focus groups, and student course evaluations are used to evaluate these courses and to provide continuing feedback for improvement over two implementation cycles. Pre- versus postsurvey data indicate that students gain self-efficacy in scientific inquiry skills and develop more expert-like perceptions of biology. These gains are more significant and have larger effect sizes in the second implementation year, a trend also supported by qualitative data. Together, these data indicate a progression of improvement of efficacies of these CUREs.