The development of stop consonant voicing in English-speaking children has been documented as a progressive mastery of phonological contrast, but implementation of voicing within one voicing category has not been systematically examined. This study provides a comprehensive account of structured variability in phonetic realization of /b/ in running speech by 8–12-year-old American children (n = 48) when compared to adults (n = 36). The stop always occurred word-initially, was followed by either a voiced or voiceless coda, and its position varied in a sentence, which created systematic conditions to examine acoustic variability in closure duration (CD) and voicing during the closure (VDC) stemming from phonetic context and prosodic prominence. Children demonstrated command of long-distance anticipatory coarticulation, providing evidence that information about coda voicing is distributed over an entire monosyllabic word and is available in the onset stop. They also manifested covariation of cues to stop voicing and command of prosodic variation, despite greater random variability, greater CD, reduced VDC, and exaggerated execution of sentential focus when compared to adults. Controlling for regional variation, dialect was a significant predictor for adults but not for children, who no longer adhered to the marked local variants in their implementation of stop voicing.