The current study reports the results of a randomized controlled trial examining the impact of the Getting Ready parent-engagement intervention on expressive language skills of children (N = 267) with developmental concerns upon entry into preschool. Latent growth for expressive language and moderating roles of parental stress and parental involvement in learning at home were analyzed using a structural equation modeling framework. Probing of interaction effects indicates that when families report below-average levels of stress or involvement in learning at home, children in the intervention group demonstrate accelerated growth in expressive language skills compared with peers in the comparison condition. Getting Ready is most salient when families report low to moderate levels of stress and can serve as a buffer for families who report low to moderate levels of involvement in learning at preschool entry. Results have implications for connections between families and educators across the preschool period.