In 2012, Cleveland State University implemented a comprehensive program, called Operation STEM (OpSTEM), funded by two National Science Foundation grants, federal work study, and Cleveland State University. Its goal is to increase retention and graduation rates among Science, Technology, Engineering, and Mathematics (STEM) students by helping them complete the precalculus-calculus sequence successfully. OpSTEM targets freshmen pursuing STEM majors who are members of minority groups that are underrepresented in STEM, and/or first-generation college students. The majority of OpSTEM Scholars begin their mathematics coursework at the beginning of the precalculus sequence. OpSTEM provides these students with many services: a two-week summer institute, mandatory supplemental instruction, project-based instruction, mentoring, STEM speakers, free summer calculus, college success workshops, social activities, and stipends based on participation in these activities and successful completion of coursework. The implementation of the OpSTEM program created an experimental design with two treatment groups, where one group received all the treatments and one group received only mandatory supplemental instruction. They were both compared to a control group from before OpSTEM began. Student data collected have demonstrated that mandatory supplemental instruction alone is effective at increasing the pass rate for precalculus courses, and the additional services and incentives provided the other treatment group increases the pass rate even further. This is especially significant because the population that received all the services (OpSTEM Scholars) is a population that is more at-risk than the typical population. The ultimate goal of OpSTEM is to increase retention and completion among STEM students by helping them succeed in the precalculus-calculus sequence. Additional time is needed to assess the rates at which these students are completing STEM degrees, but preliminarily data show that OpSTEM Scholars' retention rate is higher than the university's retention rate as a whole and higher than the university's retention rate in STEM fields in particular.