This paper describes the development of a Peer-Led Guided Inquiry (PLGI) program for teaching calculus at the University of South Florida. This approach uses the POGIL (Process Oriented Guided Inquiry Learning) teaching strategy and the small group learning model PLTL (Peer-Led Team Learning). The developed materials used a learning cycle based on three phases of inquiry: exploration of a model, concept invention, and application. Fifty minutes weekly of lecture in Engineering and Life Sciences Calculus were replaced by the PLGI curriculum, where students worked in groups with peer leaders as instructors. The main outcomes measured were pass and withdrawal rates for sections using this approach compared to historical and concurrent sections not using PLGI. Our results showed higher pass rates in Life Sciences Calculus (18% gain in comparison to historical sections and 8.2% gain in comparison to concurrent non-PLGI sections). In Engineering Calculus, we also saw higher pass rates for PLGI sections (18.2% gain in comparison to historical rates and 4.0% gain in comparison to concurrent non-PLGI sections). Withdrawal rates also declined for both Life Sciences and Engineering Calculus. Both sexes had greater pass rates and lower withdrawal rates in both types of calculus. PLGI sections showed higher pass rates for African-American students in life sciences (16.5% gain in comparison to historical sections and 8.7% gain in comparison to concurrent non-PLGI sections). The impact of PLGI for African- American students was more dramatic in Engineering Calculus (24.9% gain in comparison to historical sections and a 17.6% gain in comparison to concurrent non-PLGI sections).