Cosmopoulos has given over 200 public lectures (including Keynote Addresses) on various topics of Greek and Roman art, archaeology, history, religion, and culture, as a National and McDonald Speaker for the Archaeological Institute of America and also as an invited speaker (list of universities and institutions below). In addition, he had made numerous presentations  to elementary, middle-schools, and high schools of the Winnipeg and St. Louis School Divisions, as well as to diverse private groups, such as The English Speaking Union, the Rotary Club, etc.

CANADA. University of Manitoba, McGill University, Winnipeg Art Gallery, Toronto City Hall, University of Calgary, University of Alberta, University of Toronto, University of Saskatchewan, Brock University, Royal Ontario Museum.

USA. University of Missouri-St. Louis, University of Missouri-Columbia,Washington University in St. Louis, Webster University, St. Louis Art Museum, Missouri History Museum, St. Louis County Libraries, Boston University, Brown University, Bryn Mawr College, Chicago Art Institute, Cornell University,  Detroit Institute of Arts, Field Museum Chicago, New York University, Rice University, University of Arizona, Wooster College,University of Miami, University of Nevada-Las Vegas,  Univ. of Texas at Austin, Johns Hopkins University, Denison University, Emory University, University of Cincinnati; also various local chapters of the Archaeological Institute of America.

GREECE. Athens Archaeological Society, Canadian Academic Institute at Athens, American School of Classical Studies at Athens.