Purpose: We investigated developmental differences in a dual task involving rhyming and tone judgment/decisions and the effects of varying cognitive demands on task performance. Method: Participants were 7- to 11-year-olds, 12- to 15-year-olds, and adults between 18 and 40 years (n = 19 per group). The rhyming task consisted of three stimuli categories (nonrhyme, rhyme, and replica), and the tone task stimuli were presented at short (100 ms) versus long (900 ms) stimulus onset asynchrony (SOA) from the onset of the rhyme task to vary cognitive demands. Response time (RT) and error data were analyzed using linear and binomial mixed-methods analysis, respectively. Results and Conclusions: Adults did not show an SOA-based effect in rhyming RT, while the 12- to 15-year-olds showed the most effect (RT, long > short SOA). Response to the replica category was significantly faster than for the other categories in all age groups. A reverse SOA effect was evident in the tone task (RT, short > long SOA) in all age groups. The 7- to 11-year-olds showed twice the task switch cost effect in the tone task RT. Age grouping and phoneme awareness were significant predictors of performance in both tasks, and additionally, SOA was a significant predictor of performance in the secondary task. The findings have implications for: (1) understanding maturational differences in rhyming and executive control for dual tasking and the cognitive mechanisms supporting such effects; and (2) identifying variables contributing to the developmental differences.