This article is a result of the analysis of student-level enrollment records from twenty-one research universities in the United States, and it contributes to a more robust understanding of timely completion of STEM doctorates by underrepresented minority students. Using multivariate logit regression models, findings indicated that Hispanic/Latino and students from other underrepresented groups complete at higher rates than do their Black/African American counterparts. Findings also indicated that prior master's degrees and institutional participation in doctoral completion programs positively correlate with STEM doctoral completion. We conclude by offering insights and recommendations for graduate schools about how to increase the STEM doctoral attainment rate of students from underrepresented groups.