Purpose The purpose of this article was to provide the reference data and evaluate psychometric properties for the percent grammatical utterances (PGU; Eisenberg & Guo, 2013) in children between 4 and 9 years of age from the database of the Edmonton Narrative Norms Instrument (ENNI; Schneider, Dubé, & Hayward, 2005). Method Participants were 377 children who were between 4 and 9 years of age, including 300 children with typical language (TL) and 77 children with language impairment (LI). Narrative samples were collected using the ENNI protocol (i.e., a story generation task). PGU was computed from the samples. Split-half reliability, concurrent criterion validity, and diagnostic accuracy for PGU were further evaluated. Results PGU increased significantly in children between 4 and 9 years of age in both the TL and LI groups. In addition, the correlation coefficients for the split-half reliability and concurrent criterion validity of PGU were all large (rs ≥ .557, ps < .001). The diagnostic accuracy of PGU was also good or acceptable from ages 4 to 9 years. Conclusions With the attested psychometric properties, PGU computed from the ENNI could be used as an assessment tool for identifying children with LI between 4 and 9 years of age. The reference data of PGU could also be used for monitoring treatment progress. Supplemental Material https://doi.org/10.23641/asha.9630590.