The present study examines the use of lexical bundles in first year core engineering textbooks, identifies vocabulary-based discourse units (VBDUs) in the textbooks, and explores the connections between lexical bundles and the VBDUs. A first year core engineering textbook corpus (FCETC) consisting of 995,672 running words was compiled with materials drawn from seven textbooks required in a first-year engineering undergraduate program. A total of 95 lexical bundles were identified in the FCETC. Lexical bundles in the corpus are more often phrasal than clausal. These bundles mainly serve as referential bundles, discourse organizers, and stance bundles. These bundles allow authors to take on the role of experts who deliver foundational knowledge in a professional way and enable the authors to act as facilitators who make the content accessible and involve readers in their learning processes. The comparison of the use of lexical bundles in first year core engineering textbooks, electrical engineering introductory textbooks, university teaching, and university textbooks indicates that disciplinary specificity and genres impact the use of lexical bundles in the four registers. A total of 665 VBDUs were identified in 14 chapters randomly selected from the FCETC. These VBDUs fall into five main categories, which include explaining VBDUs, presenting VBDUs, solving VBDUs, introducing VBDUs, and bridging VBDUs. Single or multiple VBDUs construct four types of macro-processes for knowledge construction, which suggest that the authors focus on the procedures and steps and guide learners to appropriately approach the theories and understand problem-solving operations. This study also shows that the communicative purposes of VBDUs determine the distribution of lexical bundles in these discourse units. The use of lexical bundles differs in the categories and subcategories of VBDUs and helps achieve various communicative purposes of the VBDUs. Furthermore, this study identifies textual colligations of lexical bundles in the engineering textbooks: the authors avoid using stance bundles in introducing VBDUs and rarely use discourse organizers in introducing VBDUs and bridging VBDUs. Findings of this study can provide pedagogical resources to improve learners' reading and writing competencies in the field of engineering.