We used the timing of serial recall in several situations to reveal important aspects of recall groupings that participants construct and the reasons those groupings occur. We examined the timing of responses in the recall of digit strings within two published experiments. Cowan, Saults, Elliott, and Moreno (2002) examined memory for nine-item lists in a way that deconfounded the presentation modality, input versus output serial position (using a varied starting point of recall), memory load from items not yet recalled (using whole vs. partial recall), and the presence or absence of the temporal grouping of the lists into triads. Accuracy was strikingly different in the two modalities, with grouping drastically changing recall of acoustic lists but with little difference between grouped versus ungrouped visual lists. Despite the modality difference in recall, the present timing results show that participants imposed a similar grouped structure in recall for both modalities. When errors were made, the original grouping structure still was maintained in the output timing. Cowan et al. (2005, Experiment 1) presented ungrouped acoustic lists of varying lengths in a span task. In this case, there was never a grouping structure presented to the participant and the accuracy data did not reveal evidence of grouping, but we show clear grouping in the timing structure. This grouping structure varied with both the list length and an individual's span. Timing in both experiments shows that a grouping structure is imposed on responses in a manner that is dependent on several factors not present in the stimuli.