The efficacy and consequential validity of an ecological approach to behavioral intervention with families of children with developmental disabilities were examined. The approach aimed to transform coercive into constructive parent–child interaction in family routines. Ten families participated, including ten mothers and fathers and ten children 3–8 years old with developmental disabilities. Thirty-six family routines were selected (2–4 per family). Dependent measures included child problem behavior, routine steps completed, and coercive and constructive parent–child interaction. For each family, a single case, multiple baseline design was employed with three phases: baseline, intervention, and follow-up. Visual analysis evaluated the functional relation between intervention and improvements in child behavior and routine participation. Nonparametric tests across families evaluated the statistical significance of these improvements. Sequential analyses within families and univariate analyses across families examined changes from baseline to intervention in the percentage and odds ratio of coercive and constructive parent–child interaction. Multiple baseline results documented functional or basic effects for 8 of 10 families. Nonparametric tests showed these changes to be significant. Follow-up showed durability at 11–24 months postintervention. Sequential analyses documented the transformation of coercive into constructive processes for 9 of 10 families. Univariate analyses across families showed significant improvements in 2- and 4-step coercive and constructive processes but not in odds ratio. Results offer evidence of the efficacy of the approach and consequential validity of the ecological unit of analysis, parent–child interaction in family routines. Future studies should improve efficiency, and outcomes for families experiencing family systems challenges.