Many biochemistry laboratory courses expose students to laboratory techniques through pre-determined experiments in which students follow stepwise protocols provided by the instructor. This approach fails to provide students with sufficient opportunities to practice experimental design and critical thinking. Ten inquiry modules were created for a one-semester undergraduate biochemistry laboratory course; these are freely available on the project website. A slightly modified version of the Experimental Design Ability Test (EDAT) was used to assess the impact of inquiry-based learning on student experimental design ability in four experimental (inquiry) and four control (cookbook) sections. EDAT is a published tool that has been validated for use in undergraduate populations. The results, measured by pre- and post-tests, showed a significant positive impact on the experimental design ability of students in sections that employed the inquiry approach, when compared to those in control sections that employed the cookbook approach. A follow-up conversation with students in a sequel course suggested that the inquiry-based approach also benefited students by promoting self-directed learning.