Mechanisms translating initial impacts of early childhood education (ECE) programs into longer-term effects are poorly understood. This article posits that the temporality of unobserved mediated effects are integral to our understanding of the pathways underlying ECE programs’ long-term impacts. Leveraging panel data, we examined the patterns of indirect effects from two ECE programs on educational attainment via bundled mediators measured at age 8 or 10, 12, and 15 (the Abecedarian Project: N =107; 97% Black; 3% White; 52% girls. Head Start: N = 1,251; 44% Black; 25% Hispanic; 31% White; 50% girls). Accounting for up to 50% of the impact, indirect effects in both studies revealed stable patterns of direct effects, suggesting that impacts on unmeasured mediators were present throughout the duration of the period after the end of ECE programs and before later outcomes were observed. These findings indicate that some of the mechanisms involved in Abecedarian's and Head Start's long-term impacts were substantial and independent from those typically captured by commonly used measures of cognitive and socioemotional or behavioral skills, which points to the need for new approaches to studying child-environment transactions. (author abstract)