Roughly half of 4-year students who begin as STEM majors either change to non-STEM majors or drop out of college altogether. STEM attrition is especially disconcerting for underserved students, such as people of color or individuals from low-income families, who are significantly less likely to persist in or graduate from a STEM degree program when compared to their White or higher-income peers. Previous researchers have reported that co-enrolling at more than one institution (or swirling between institutions) can be associated with higher rates of persistence and graduation. In this study, we leverage student-level transcript data from a high enrollment, broad-access university to examine the influence of math swirling on underserved students' academic outcomes within high-demand STEM degree programs. We find that math swirling is positively related to persistence to upper-division math courses and bachelor's degree completion in non-STEM degree programs, but math swirling has no influence on students' likelihood of bachelor's degree completion in high-demand STEM fields.