Early childhood education and care (ECEC), involving nonparental preschool supervision and programming for children in centre-based and school contexts, can influence academic outcomes during elementary years. We present preliminary findings identifying quantity and timing as important but relatively little investigated aspects of ECEC experience. We focus on associations among cumulative ECEC hours during the early preschool (birth to 24 months prior to the commencement of Grade 1) and late preschool (24 months prior to Grade 1) periods, and later growth in children's achievement in letter naming, decoding, and reading comprehension. Ninety-four children, aged 72 to 91 months at the outset, were examined across five testing occasions spanning the first two-and-a-half years of formal schooling. The quantity of ECEC in the early and late periods did not independently account for significant variance in initial status or growth in reading outcomes. However, differential influences of timing and quantity in children at risk of developing reading difficulty and in children experiencing family SES risk were found for decoding and comprehension. Results are consistent with a contextual support model of influence of ECEC quantity, and they indicate contextual circumstances in which ECEC experience may be a protective factor for early reading development. (author abstract)