Criminal justice researchers have studied caseload size to determine whether smaller caseloads improve probation outcomes. With exceptions, these findings have shown that reduced probation officer caseloads have not reduced criminal recidivism for high risk probationers and have increased revocation rates. One explanation is that officers with reduced caseloads do not materially change their supervision practices when caseloads are reduced, either failing to achieve increased supervision or failing to improve treatment intervention or both. This raises the question: Would reduced caseloads improve supervision outcomes for medium to high risk offenders in a probation agency that trains its officers to apply a balance of controlling and correctional/rehabilitative measures? The logic is that the reduced caseload would allow probation officers to better deliver correctional interventions, thereby reducing recidivism without unduly increasing revocations. The research answered this question in three purposefully selected probation agencies: Oklahoma City, where we implemented a randomized controlled trial experiment; Polk County, Iowa, where we implemented a regression discontinuity design study, and four judicial districts in Colorado. The results showed that reducing probation officer caseloads can reduce criminal recidivism when evidence based practices are implemented. The results suggest that reduced caseloads can lead to improved recidivism outcomes when evidence based practices trained officers with reduced caseloads are better able to identify treatment needs among their clientele, and thus better able to direct resources to those most in need. Consequently, reduced caseloads result in more efficient distribution of resources, and improved average probation outcomes. This study did not demonstrate the efficacy of the full complement of evidence based practices. Nevertheless, the implication is that evidence based practices mattered: the literature demonstrates that without evidence based practices reduced caseloads do not reduce recidivism.