This article investigates the implementation of inquiry-oriented instruction in 20 undergraduate mathematics classrooms. In contrast to conventional wisdom that active learning is good for all students, we found gendered performance differences between women and men in the inquiry classes that were not present in a noninquiry comparison sample. Through a secondary analysis of classroom videos, we linked these performance inequities to differences in women's participation rates across classes. Thus, we provide empirical evidence that simply implementing active learning is insufficient, and that the nature of inquiry-oriented classrooms is highly consequential for improving gender equity in mathematics.