Purpose: This feasibility study examines the convergent and divergent validity of the Grammaticality and Utterance Length Instrument (GLi), a tool designed to assess the grammaticality and average utterance length of a child's prerecorded story retell. Method: Three raters used the GLi to rate audio-recorded story retells from 100 English-speaking preschool children. To examine convergent validity, the results of the GLi were correlated with 2 language sample measures, mean length of utterance in words and percentage of grammatical utterances, and with the results of the Structured Photographic Expressive Language Test-Third Edition (Dawson, Stout, & Eyer, 2003). To examine divergent validity, the results of the GLi were correlated with the results of the Kaufman Brief Intelligence Test-Second Edition (Kaufman & Kaufman, 2004). Comparisons between task completion time for the GLi and Systematic Analysis of Language Transcripts (SALT; Miller & Iglesias, 2010) transcription and analysis were also conducted. Last, preliminary discriminant analysis was used to examine the diagnostic potential of the GLi. Results: The results of this study provide evidence of convergent and divergent validity for the GLi. The task completion time for the GLi was considerably shorter than the SALT transcription and analysis. Preliminary analysis of diagnostic accuracy suggests that the GLi has the potential to be a good tool to identify children with language impairment. Discussion: The GLi has good convergent and divergent validity and is a reliable instrument to assess utterance length and grammaticality of prerecorded language samples. However, SALT transcription and analysis provide a more detailed and comprehensive analysis of the language skills of a child.