The low number of women that persist in science, technology, engineering, and mathematics (STEM) disciplines is a current problem that has manifested particularly in the engineering collegiate environment. Regardless of previous levels of academic achievement, women are more likely to leave engineering than their male counterparts. Self-efficacy, or the self-confidence to complete certain tasks, is attributed to attrition and persistence in engineering programs. STEM intervention programs that focus on improving the self-efficacy of students can lead to women's persistence in engineering programs. This study utilizes Bandura's SelfEfficacy Theory to investigate the relationship between engineering students' reports of the benefits of participating in a university STEM intervention program and self-efficacy in engineering, and how this changes over the first year of college. Preliminary findings indicate that women and men's engineering major confidence significantly increases after participation in the pre-college summer transition program. However, by the end of students' first academic year, their engineering major confidence is comparable to the levels reported prior to their participation in the summer program. These findings partially align with the extant literature on women's engineering efficacy but suggest the need for further investigation.