Young English-speaking children often produce utterances with missing 3sg -s (e.g., *He play). Since the mid 1990s, such errors have tended to be treated as Optional Infinitive (OI) errors, in which the verb is a non-finite form (e.g., Wexler, 1998; Legate & Yang, 2007). The present article reports the results of a cross-sectional elicited-production study with 22 children (aged 3;1-4;1), which investigated the possibility that at least some apparent OI errors reflect a process of defaulting to the form with the highest frequency in the input. Across 48 verbs, a significant negative correlation was observed between the proportion of "bare" vs. 3sg -s forms in a representative input corpus and the rate of 3sg -s production. This finding suggests that, in addition to other learning mechanisms that yield such errors cross-linguistically, at least some of the OI errors produced by English-speaking children reflect a process of defaulting to a high-frequency/phonologically simple form.