Researchers have found no agreement on whether dual-task interference in language performance, such as dual-task interference from tone discrimination on picture naming, reflects passive queuing or active scheduling of processes for each task. According to a passive-queuing account, while a central response-selection bottleneck is occupied by the tone discrimination task, picture naming is held in a passive queue until the bottleneck is freed. In contrast, according to an active-scheduling account, participants determine the order in which the tasks proceed, monitor progress on the tasks, suspend picture naming and hold it in working memory, and determine when to resume picture naming. Here, we report a study that assessed the relative merits of the queuing and scheduling accounts by examining whether the magnitude of dual-task interference in picture naming is associated with individual differences in the capacity of monitoring and updating of working memory representations, as assessed by the operation-span task. We observed that the updating/monitoring ability correlated with the speed of picture naming and with the magnitude of the interference from tone discrimination on picture naming. These results lend support to the active-scheduling account of dual-task interference in picture naming.