INTRODUCTION: Previous studies suggest that youth may follow temporal patterns of physical activity (PA). Research has provided evidence for both the compensatory and synergistic effects of PA among youth. It is unclear, however, how the presence of a PA intervention may play a role in children’s normal patterns of physical activity. PURPOSE: To determine if the Girls on the Move intervention influenced the proportion of girls obtaining various levels of afterschool PA vs. during-school PA between intervention and control schools. METHODS: MVPA minutes were measured via accelerometers worn at the right hip for 7 days (5 weekdays, 2 weekend days). Monitors were set to start recording data at 5 A.M. on the day after distribution to at both the intervention and control schools. Data for the vertical axis were re-integrated to 15-s epochs and processed using Evenson cut-points. Average MVPA/hr was calculated from accelerometer data. MVPA was assessed at three different timepoints (e.g. pre-intervention, post-intervention, and 9-month follow-up) and examined for two time-blocks (during school, after school). RESULTS: Chi-square tests were performed to assess significant differences in the proportion of girls who achieved higher average MVPA/hr during school and girls who achieved higher average MVPA/hr after school in the intervention and control schools. The Chi-square test was not significant at baseline (χ²=1.67, p=0.2, α=0.05), but was significant for both the post-intervention and 9-month follow-up, with the intervention group having a higher proportion of girls getting more PA after school (χ²=14.82, p=.00014, α=0.05, χ²=9.89, p=.0017, α=0.05, respectively). CONCLUSION: The Girls on the Move intervention significantly increased the proportion of girls who achieved higher average MVPA/hr after school compared to the girls in the control schools (synergistic effect of the intervention). These results suggest an after-school PA intervention may be effective in increasing girls’ PA after school even after the completion of the intervention. This study may inform future PA interventions to examine changes to temporal patterns (e.g. how much PA youth are getting during specific times of the day) in addition to total overall PA.