Corpus-based studies of lexical bundles have opened new avenues for language teaching research. The fact that naturally occurring language consists of patterns of lexical repetition and multi-word units has given rise to the question of chunkiness in learner language. This study was designed to examine lexical bundles and their functions in a small, specialized learner corpus of opinion paragraphs written by Saudi English as a Foreign Language (EFL) students at the University of Jeddah. The study takes a frequency-driven approach to identify common lexical bundles. A learner corpus of 237 writing tasks produced by Saudi undergraduate students from 11 different sections is compiled and explored. The primary aim was to identify high-frequency five-word lexical bundles and explore their functions in the learner corpus, as well as investigate any distributional differences in bundle use across the various student sections. The findings revealed that learners utilized lexical bundles primarily to serve four key functions: expressing stance, supporting a point, introducing an item, and making recommendations. Notably, variations were observed in the distribution of these functional categories among the different student groups. The study concludes by outlining some pedagogical applications for educators and language practitioners, highlighting the value of learner corpus-informed approaches to enhancing learners' awareness and mastery of lexical patterning in academic writing. By better understanding the role of formulaic language in learner production, instructors can tailor their teaching to more effectively support students' linguistic development.