This study aimed to evaluate Promoting Reciprocal Relationships with Flexibility, Coaching, and Teaching (PRRFCT Match), a parent-mediated naturalistic developmental behavioral intervention package. An expansion from an earlier pilot study (see Kunze et al., 2021), PRRFCT Match incorporates virtual coaching between a novice coach and parent to implement evidence-based, applied behavior analytic (ABA) techniques during play to increase engagement and decrease unengaged behavior exhibited by their young child with developmental delays (26-50 months old). Ten parent-child dyads were matched with a coach in this concurrent multiple baseline design across participants. Simulating the clinical training level of a novice early interventionist, nine graduate student clinicians received training as coaches on PRRFCT Match implementation and weekly supervision by a research team member. All aspects of training and intervention were delivered virtually. A visual analysis of the data combined with Tau-U revealed a strong basic effect between clinician coaching and parent strategy use. For child participants, a visual analysis and Tau-U results suggest that most increased engagement and decreased their unengaged behavior during the intervention. High variability, overlap, and high engagement at baseline are discussed. This study shows promise for the PRRFCT Match intervention package. The ABA technologies mediated by parents during play increased child engagement and decreased unengagement for most participants.