Three preK–6 U.S. university methods instructors-researchers (literacy, science, social studies) joined 17 Title I school teachers for collaborative lesson planning and teaching within the preK–5 school setting. Each team’s goal was to create and teach interdisciplinary curriculum units using U.S. English language arts Common Core State Standards with social studies and science. A year-long instrumental case study design was used to examine (a) how teachers perceived collaborative professional development to create interdisciplinary unit plans and (b) how teachers viewed outcomes of teaching interdisciplinary units of their own design. Practice articles regarding Common Core State Standards curricula integration are plentiful; however, this study offers researched insights.Collectively, research from various locations and school cultures benefits those needing to structure realistic professional development designs