Reading typically undergoes a qualitative shift around Grade 4, becoming more fluent and silent, but there is no established measure for fluency in children's silent reading. The present study presents a measure of self-paced reading in children, examining the use of complexity measures for time-series analyses recently established with adults. Cross-sectional groups of adults and children in Grades 2, 4, and 6 read the same passage of a Grade 2-level story, either silently or aloud. The dynamical structure of fluency in reading times was explored with fractal and recurrence quantification analysis. Results revealed that more fluent reading (with increasing age) was marked by greater structure and stability and that oral reading compared with silent reading showed less fractal structure, indicating silent reading as a more flexibly stable, adaptive coordinated behavior. The complexity metrics show promise for an alternate way to characterize reading fluency.