Although metacognition is considered a central aspect of self-regulated learning and is often linked to learning outcomes, little is known about the intraindividual development and factors that lead to developmental improvement over time. This longitudinal study investigated 2nd graders' (N = 119, aged 8-9 years) metacognitive monitoring and control abilities in the context of spelling. Children were tested at the beginning (T[subscript 1]) and at the end of their 2nd school year (T[subscript 2]). The study focused on the development of monitoring and control, their interplay at both measurement points and across time, and the cross-sectional and longitudinal impact of 1st-order task performance (here, spelling) on the 2 metacognitive processes. Results revealed substantial developmental progression in most monitoring and control measures. Monitoring and control were interrelated cross-sectionally only at T[subscript 2], but longitudinally, control predicted monitoring. Interestingly, earlier spelling performance predicted not only later spelling, but also later monitoring and control abilities. The findings indicate that earlier domain-specific skills in the 1st-order task (i.e., spelling) are 1 of several possible driving forces for metacognitive development.