Using institutional data from University of California, Merced (UC Merced), this dissertation explores the relationship between enrolling in academic units in the summer term immediately after the first year of college (first-summer) and four-year degree completion at a Hispanic- and Minority-Serving Institution, through the lenses of Academic Momentum research and the theory of student engagement in the Educational Interface. A number of variables are considered, including student demographic and academic characteristics, as well as student first-year academic success, which is defined using cumulative first-year GPA and unit accumulation. Specific populations of interest include First- generation, Pell-eligible, URM, and STEM students. Students who are First-generation or URM were found to be less likely to enroll in first-summer, while STEM students were more likely to enroll, as were students who experienced greater academic success in terms of GPA and unit accumulation in their first year of college. Overall, first-summer was associated with a statistically significant increased likelihood of four- year degree completion, especially for STEM students, but the association changed when controlling for varying levels of first-year academic success. The strongest associations between first-summer and four- year degree attainment were found with students in the lowest or highest first-year Academic Success Groups. The association of first-summer and four-year degree completion for students who earned at least a 2.0 first-year GPA but did not complete 30 academic units in the first year was positive but not statistically significant. However, further exploration of this group found first-summer to be positive and significant for STEM students and students who entered as an Undeclared major. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]