Introduction. Afterschool programs (ASPs) across the US are working towards achieving the standard of all children accumulating 30 min of moderate-to-vigorous physical activity (MVPA) during program time. This study describes the two-year impact of an intervention designed to assist ASPs meeting the 30 min/day MVPA standard. Methods. Using a two-year delayed treatment, group randomized controlled trial, 20 ASPs serving [approximately] 1700 children/year (6-12 yrs) were randomized to either an immediate (n = 10, baseline-2013 and 2 yrs intervention fall-2013-to-spring-2015) or delayed group (n = 10, baseline 2013-2014 and 1 yr intervention fall-2014-to-spring-2015). The intervention, Strategies-To-Enhance-Practice (STEPs), focused on programming MVPA in the daily schedule, training of staff and leaders, and ongoing technical support/assistance. Accelerometry-derived proportion of children meeting the 30 min/day MVPA standard was measured in the spring of each year. Mixed model logistic regressions were used to examine the change in the odds of achieving the MVPA standard. Analyses were conducted in 2015. Data were collected in one southeastern US state. Results. Immediate boys (n = 677) and delayed girls (n = 658) increased the percent achieving 30 min MVPA/day from 35.9% to 47.0% (odds ratio [OR] = 1.88, 95% CI 1.18-3.00) and 13.1% to 19.1% (OR = 1.42, 95% CI 1.03-1.96). Immediate girls (n = 613) and delayed boys (n=687) exhibited a nonsignificant increase from 19.1% to 21.6% (OR = 1.20, 95% CI 0.84-1.72) and 29.0% to 31.3% (OR = 1.13, 95% CI 0.80-1.58). Conclusions. STEPs can have an impact on children's MVPA and time spent sedentary, yet was unable to fully achieve the goal of all children accumulating 30 min MVPA/day. Additional efforts are need to identify strategies ASPs can use to meet this important public health standard. (author abstract)