Many students who enroll in a public U.S. 4-y college will not graduate. The odds of completing a college degree are even lower for students who have been marginalized in higher education, especially in Science, Technology, Engineering, and Math (STEM) fields. Can undergraduate research increase a student's likelihood of graduating college and close educational equity gaps in college completion? To answer this question, we use data from six public U.S. universities (N = 120,308 students) and use Propensity Score Matching to generate a comparison group for analyses. We conducted logistic regressions on graduation rates and equity gaps in 4 and 6 y using the matched comparison group and undergraduate researchers in STEM (n = 2727). When being compared with like-peers and controlling for background characteristics and prior academic performance, students who participated in undergraduate research were twice as likely to graduate in 4 y and over 10 times as likely to graduate in 6 y. We also found that equity gaps in 4-y graduation rates for students of color, low-income, and first-generation students were cut in half for undergraduate researchers. At 6 y, these gaps were completely closed for undergraduate researchers. As we seek ways to close education gaps and increase graduation rates, undergraduate research can be a meaningful practice to improve student success.