Concerning the marginalization of computer science education in K-12 STEM education in the United States, this study examined the extent to which taking more credits in computer science courses at the secondary level predicts students' STEM major choices in postsecondary institutions in the U.S., by comparison to the well-documented predictors of students' STEM major choices after controlling for student demographic characteristics (i.e., gender, SES, and racial background). These predictors include credits earned in math and science courses as well as ACT math scores. Drawing on a nationally representative sample of U.S. young adults who were 12th graders in 2004 and disclosed their college majors by 2006, logistic regression analyses revealed that students who took more units in computer science courses were significantly more likely to choose STEM majors in both 4-year and 2-year postsecondary institutions. Moreover, regardless of the type of postsecondary institutions that students attended, taking more units in computer science courses played a significant role in choosing STEM majors. In addition, the effects of computer science education on student STEM major selection were equally as strong as the effects of math and science education. The results suggest that promoting the quality of computer science education is just as important in motivating students to pursue STEM education and career choices at the secondary level as are math and science education.