Research has indicated that lexical richness is an important indicator of second language (L2) proficiency. However, most research has examined written, cross-sectional English L2 corpora and does not necessarily indicate how spoken lexical use develops over time or whether observed trends are stable across L2s. This study adds to previous research on the development of spoken vocabulary by investigating lexical features of L2 Spanish learners over a 21-month period, using the LANGSNAP corpus. Multiple lexical richness indices used in previous studies were examined including lexical diversity, word frequency, word concreteness, and bigram strength of association. Linear mixed-effects models were run to examine changes over time. The results suggest that although some features of lexical richness (e.g., word frequency) see meaningful change over time, others (e.g., bigram T score) may not be indicative of L2 oral development.