Ordering of information is a critical component that underlies several cognitive functions. Prefrontal theta-gamma coupling (TGC) is a neurophysiologic measure associated with ordering of information during the performance of a working memory task (N-back). Little is known about the relationship between TGC and ordering during other cognitive tasks or whether the relationship between TGC and ordering of information is independent of clinical condition. This study aimed to determine whether the relationship between TGC and ordering of information exists independent of a task and its timing, and whether this relationship is the same in different clinical conditions. A total of 311 participants were assessed using a neuropsychological battery that included the N-back during which TGC was measured; two other tasks that also require ordering; and three tests that do not require ordering. All non-N-back tasks were completed several days separate from the N-back by a mean interval (SD) of 5.14 (8.03). Our three hypotheses were that TGC during the N-back task would be associated with performance on N-Back and other cognitive tasks that also require ordering, but not with performance on cognitive tasks that do not require ordering; and that these relationships will be independent of clinical diagnosis. Multivariate linear regression results show that TGC was associated with performance on the ordering tasks but not the non-ordering tasks. In addition, there was no interaction between TGC and diagnosis. Our study is the first to demonstrate that TGC is a neurophysiologic measure of ordering information across several cognitive tasks that require ordering, and this TGC-ordering relationship is stable over time even when several days separate the measurement of TGC and the performance of the ordering tasks. Our results also show that this relationship is independent of clinical diagnosis, supporting the brain-behavior nature of this relationship. These results highlight the importance of TGC in ordering-based cognition, and suggest that TGC could be a valid target for interventions that aim to enhance this function across cognitive tasks and clinical conditions.