This study assesses lexical density in the written performance of a controlled sample of Saudi undergraduates majoring in English as a Foreign Language (EFL). It explores the relationship between lexical density and the quality of written performance by measuring lexical density in sample texts of learner's final exams. Linguistic content analysis was used on these texts to categorize terms and to find links between them. Each document’s functional and content terms were counted and divided by the total words in the text to compute lexical density. The study reveals that the lexical density in the written performance of Saudi EFL undergraduates is categorized as less dense than that of their higher-level peers, indicating an increase in lexical density as students are upgraded to higher levels of study. The lexical density varies according to a learner’s proficiency because the data obtained show differences between the lexical density scores of the two samples. The findings also suggest that the length of a text does not always imply that the content is lexically rich. The study provides evidence of the possibility of improving EFL learners’ reasoning performance when this performance is characterized by lexical density. The study urges that raising teachers’ awareness about lexical density and how it affects writing could also be a pedagogical implication of the current study.