He teaches graduate degree courses in public administration in strategy, leadership, and governance. He has been funded for research projects on governance from the Haynes Foundation, Bedrosian Center on Governance, and has a Fulbright Specialist Program award for teaching leadership, institutional design, and governance in Istanbul, Turkey. Additionally, he works with universities in the states of Vera Cruz, Aguascalientes, and Yucatan, Mexico. Formerly, Callahan directed and taught in leadership and graduate degree programs in Los Angeles and Sacramento for 13 years for the University of Southern California, including as director of a 10-year engagement with the Sierra Health Foundation for developing nonprofit leaders.