Purpose: This study examines the written language samples of fifth grade English learner (EL) students with and without diagnosed language-based learning disabilities (LLDs) in an effort to explore the utility of such supplemental materials for aiding in differential diagnosis of ELs with and without LLDs. Method: This sample of 127 fifth grade students consisted of ELs without identified disabilities (n = 89) and ELs diagnosed with LLDs (n = 38). Written language samples from a classroom-based expository writing task were coded for grammaticality and specific verb type of errors. An analysis of variance (ANOVA) between the groups that differed by language abilities was conducted at two time points to compare the frequency of errors and the average change in grammaticality from the beginning of the school year to the end of the school year. Results: EL students with and without LLDs performed similarly at the beginning of the school year. ELs without LLDs showed greater average change in accuracy across the school year. Significantly, higher proportions of verb tense and verb omission errors were demonstrated by ELs with LLDs when compared with their EL peers at the end of the school year. Overall grammatical accuracy was also lower for ELs with LLDs. Conclusions: Group differences at the end of the school year were confirmed in types and rate of verb errors. Results support the potential clinical utility of monitoring verb errors in writing samples over time as a supplemental tool in diagnostic evaluations and assessments for progress monitoring.