Some of their articles on this topic are:
-Laursen, S., Hassi, M.-L., Kogan, M., Hunter, A.-B., & Weston, T. (2011) Evaluation of the IBL Mathematics Project: Student and Instructor Outcomes of Inquiry-Based Learning in College Mathematics. [Report prepared for the Educational Advancement Foundation and the IBL Mathematics Centers.] Boulder, CO: Ethnography & Evaluation Research, University of Colorado, Boulder.
-Laursen, S.L., Hassi, M., Kogan, M., & Weston, T. (2014), Benefits for Women and Men of Inquiry-Based Learning in College Mathematics: A Multi-Institution Study, Journal for Research in Mathematics Education, Vol. 45, No. 4 (July 2014), pp. 406-418.
-Kogan, M. & Laursen, S.L. (2014), Assessing Long-Term Effects of Inquiry-Based Learning: A Case Study from College Mathematics, Innovative Higher Education, Volume 39, Issue 3, pp. 183--199.
The complete set of their research can be found in http://www.colorado.edu/eer/