Integrated Science, Technology, Engineering, and Mathematics (STEM) teaching provides an opportunity for students to learn STEM knowledge across two or more domains. The following study presents students' STEM content knowledge achievement after learning an integrated STEM unit taught by science and engineering technology teachers. After completing a two-week teacher professional development workshop, science and engineering technology teachers implemented an exemplar STEM unit called D-BAIT. The integrated STEM unit included entomology, biology, biomimicry, physics, and engineering design content. The researchers constructed a STEM knowledge multiple-choice pre/post-test assessment to assess students' understanding of these concepts. This study employed a quasi-experimental nonequivalent comparison group design and collected a total of 1,345 pre/post-test assessments. The data were analyzed through the independent samples t-test. The results indicate that the integrated STEM unit implemented by teacher collaboration increased students' overall STEM content knowledge. The comparison between science and engineering students' knowledge gain showed that the integrated STEM unit significantly impacts students' content knowledge. The comparisons between domain and cross-domain knowledge in science and engineering content found no significant differences; however, the mean score gain in cross-domain was higher than within the subject domain. The results of this study indicate that students can learn domain content outside of their course of study.