Numerous studies show large differences between economically advantaged and disadvantaged parents in the quality and quantity of their engagement in young children's development. This "parenting gap" may account for a substantial portion of the gap in children's early cognitive skills. However, researchers know little about whether the socioeconomic gap in parenting has increased over time. The present study investigates this question, focusing on income- and education-based gaps in parents' engagement in cognitively stimulating activities with preschool-aged children. We draw on data from four national studies conducted over 25 years. We found a decrease in income-based gaps in children's book ownership and library attendance but increasing income-based gaps for several other parent behaviors, including reading and telling stories to children and teaching children letters, words, and numbers. Income-based gaps in children's participation in out-of-home cultural activities also increased. Results for education-based gaps were similar. These gaps largely arose from top-income families pulling away from their middle- and low-income counterparts.