Team-Based Learning (TBL) uses a flipped classroom model and involves students working collaboratively in small groups, with peer assessments to promote group accountability. We implemented TBL in Calculus I in both large (N [tilde] 150) and small (N [tilde] 35) class settings. We investigated the impact of this form of instruction over two semesters (Fall 2015 and Fall 2016), and noticed improvement from the first implementation to the second. In Fall 2016, we observed many positive benefits to students, including exceptionally high class attendance, higher midterm and final exam scores than in non-TBL sections, and larger gains on the Calculus Concept Inventory than in non-TBL sections.