Contribution: This work sheds light on how classmate behaviors influence gender gaps in verbal participation in lecture-based engineering classes. It is found that after a woman participates in class, there is a temporarily increased likelihood a woman will participate again afterward. Background: Women continue to be underrepresented in STEM higher education, particularly in engineering. Positive classroom experiences are key to retaining women undergraduates, but despite research into the value of interactive teaching that allows classmates to aid each other's learning, lecturing is still most common in collegiate STEM classrooms. Research Questions: This study considers how classmates influence gender gaps in student verbal participation, even during traditional lecturing. Methodology: One thousand and three hundred and eighty seven student comments are observed over 89 class periods in ten engineering courses. The variation in student verbal participation levels with gender is analyzed, and its correlation with student speaking order, as well as other factors related to the classroom structure, is investigated. Findings: A statistically significant gender gap in class participation is observed, which is not fully explained by factors like class size or comment type. It is found, however, that when one woman participates, it increases the likelihood a woman will participate afterward, pointing to the role of classmates. This trend and the participation gender gap overall are eliminated when isolating classes taught by women. These results suggest that hearing either a woman classmate or instructor speak in class makes other women more likely to do so. As participation is linked to everything from student performance to confidence, this provides an avenue to increase gender equity in classroom experiences through small pedagogical changes that can be readily implemented into traditional lecturing.