The letter fluency task is the timed listing of words that begin with a specific letter (e.g., words starting with T). Participants often list words in phonologically related clusters (e.g., tank, task, tap) and occasionally switch clusters (e.g., tap, thud). This process has been likened to patch switching in animal foraging. Optimal performance requires switching clusters in a manner that maximizes the rate of retrieving words, known as the marginal value theorem. Previous work has found evidence for this in semantic fluency. The current study tests whether people adhere to the marginal value theorem in letter fluency and whether executive functioning is associated with optimal performance. Three letter cues (T, N, and J) and one semantic cue (animals) were administered. Results are consistent with optimal search in N and J, but not T or animals. These findings provide mixed support that people search optimally during letter fluency.