This study answered novel questions about the connection between high school extracurricular dosage (number of activities and participation duration) and the attainment of a bachelor’s degree. Using data from the Common Application and the National Student Clearinghouse (N = 311,308), we found that greater extracurricular participation positively predicted bachelor’s degree attainment. However, among students who ultimately earned a bachelor’s degree, participating in more than a moderate number of high school activities (3 or 4) predicted decreasing odds of earning a bachelor’s degree on time (within 4 years). This effect intensified as participation duration increased, such that students who participated in the greatest number of high school activities for the most years were the most likely to delay college graduation.