The purpose of this study is to investigate the use of breadth of knowledge lexical features in non-native speakers' (NNS) input and output. Our primary interest is analyzing potential breadth of knowledge lexical differences in the output of NNSs when engaged in interlanguage talk (NNS-NNS) and when engaged in naturalistic speech with a native speaker (NS). We are also interested in input differences for NNSs when engaged in interlanguage talk and when speaking with NSs To analyze these potential differences, we compare the linguistic features in spoken corpora taken from three dyads (NS-NNS, NNS-NS, NNS-NNS) using the computational tool Coh-Metrix. Our goal is to examine if lexical production differs as a function of interlocutor and examine if the findings have indications for interlanguage development. The results indicate that NNSs produce significantly greater lexical diversity and higher word frequency (i.e., more common words) in interlanguage dyads than in NNS-NS dyads. No significant differences in available NNS input were found between NS-NNS and NNS-NNS dyads. These findings have important implications for the developmental role of interlanguage speech in lexical acquisition.