The demand for preventive and easily implemented interventions to address the needs of children with significant behavioral challenges in general education settings is well-documented. First Step to Success is an evidenced-based program to address challenging behavior in preschool and elementary-school settings with a 20-year history of successful implementation (Walker et al., 1997; Walker et al., 2014b). A revision of the intervention, called First Step Next (Walker et al., 2015), was designed to (1) standardize the program components across preschool and elementary settings; (2) make the program more user friendly for implementers, including parents; and (3) increase the program's efficacy by adding new components and updating existing ones. The current study used a mixed-method approach to compare process data collected from a previous efficacy trial of the original preschool version of First Step (Feil et al., 2014) to the revised version (First Step Next; Feil et al., 2020). Overall procedural fidelity ratings were high for both program variations. Further, alliance and satisfaction ratings, as per parent- and teacher-report, were acceptable, although there were some divergent findings between parent and teacher perspectives at the item level. This study provides support for the feasibility of successfully implementing First Step Next with young children and their families in preschool settings.