Objective: This study investigates whether greater identification of mothers and fathers in different-sex couples with the stimulation dimension of intensive parenting promoted both parents' involvement in reading and benefited children's language development between ages 3 and 5 in the UK. In addition, we explore social class variations. Background: Our study tests the frequently assumed relationship of parenting beliefs about stimulation with language development, and contributes to our understanding of parenting practices and their implications for child development. Method: We draw on a large representative sample of young children from the UK Millennium Cohort Study (N = 8,071) and apply path analyses in the framework of structural equation models. Results: For mothers and fathers, stimulation beliefs partially mediated the relation between parental education and reading frequency. Mothers' and fathers' stimulation beliefs had positive effects on children’s language abilities, but their impact was small compared to the direct associations with parental education. Conclusion: While parental education emerges as a key determinant of children's language development, our study reveals the nuanced role of beliefs about stimulation within intensive parenting, prompting further investigation into the multifaceted nature of parental involvement.