Overtensing (the use of an inflected form in place of a nonfinite form, e.g. *"didn't broke" for target "didn't break") is common in early syntax. In a ChiLDES-based study of 36 children acquiring English, I examine the effects of phonological and lexical factors. For irregulars, errors are more common with verbs of low frequency and when phonological processing biases favour the past-tense form relative to the base form (vowel dominance and the consonant addition bias). For regulars, errors are more common when the inflected form ends in a rime that can occur in monomorphemic forms in English (which children have had independent practice with) than when the rime is found only in inflected forms. Results demonstrate that default patterns can be subject to lexical frequency effects. Results are compatible with a particular conceptualization of competition (the integrated multiple competitor approach), whether connectionist or symbolic.