The goal of this study was to examine initial levels and rates of change in the intensity and breadth of participation in organized activities during the adolescent years, and how these participation practices were related to youth outcomes in later adolescence. The main objectives were (a) to examine growth curves of intensity and breadth of participation from Grades 7 through 11 and their interrelations, and (b) to test the associations between these dimensions of participation and academic orientation, risky behaviors, internalizing problems, and civic development in Grade 11. A homogenous sample of 299 youth (mean age = 13.37, SD = .41; 62% girls) were surveyed annually using questionnaires and phone interviews. The main results revealed that (a) even though both intensity and breadth of participation decreased over time, intensity of participation showed steeper declines by later grades, and (b) initial levels of participation were better predictors of later outcomes than rates of change over time. Regardless of the levels of change taking place over time, results revealed that youth with high initial levels of participation (both intensity and breadth) were more committed to school and developed more positive values towards society by Grade 11 than those who participated less. This might suggest that a high level of participation during early-to-mid-adolescence is particularly important when it comes to later outcomes.