High-structure courses or flipped courses require students to obtain course content before class so that class time can be used for active-learning exercises. While textbooks are used ubiquitously in college biology courses for content dissemination, studies have shown that students frequently do not read their textbooks. To address this issue, we created preclass reading guides that provided students with a way to actively engage with the required reading for each day of class. To determine whether reading guide completion before class is associated with increased performance, we surveyed students about their use of reading guides in two sections of a large-enrollment (400+ students) introductory biology course and used multiple linear regression models to identify significant correlations. The results indicated that greater than 80% of students completed the reading guides before class and that full completion of the reading guides before class was significantly positively correlated with exam performance. Reading guides in most cases were used similarly between different student groups (based on gender, ethnicity, and aptitude). These results suggest that optional preclass reading guides may help students stay on track to acquire course content in introductory biology and thus result in improved exam performance.