We conducted an exploratory study of adult individual differences in the contents of mind-wandering experiences and in the moment-to-moment consistency of that off-task thought content within tasks. This secondary analysis of a published dataset (Kane et al., 2016) examined the content-based thought reports that 472–541 undergraduates made within five probed tasks across three sessions, and tested whether executive-control abilities (working memory capacity, attention-restraint ability), or personality dimensions of schizotypy (positive, disorganized, negative), predicted particular contents of task-unrelated thought (TUT) or the (in)stability of TUT content across successive thought reports. Latent-variable models indicated trait-like consistency in both TUT content and short-term TUT-content stability across tasks and sessions; some subjects mind-wandered about some things more than others, and some subjects were more temporally consistent in their TUT content than were others. Higher executive control was associated with more evaluative thoughts about task performance and fewer thoughts about current physical or emotional states; higher positive and disorganized schizotypy was associated with more fantastical-daydream and worry content. Contrary to expectations, executive ability correlated positively with TUT instability: higher-ability students had more shifting and varied TUT content within a task. Post hoc analysis suggested that better executive control predicted inconsistent TUT content because it also predicted shorter streaks of mind-wandering; tuning back in to task-related thought may decouple trains of off-task thought and afford novel spontaneous or cued thought content. [Data, sample analysis scripts and output, and article preprint are available via the Open Science Framework: https://osf.io/guhw7/].