He performs from materials which he himself authors and is known for his large-scale oral stories that explore the rich details and nuances of different cultures and time periods through the perceptions of a central narrative character.
After graduating from the College of the Holy Cross and unsuccessful attempts at law school and writing novels, O'Callahan found his voice as a professional storyteller in the 1970s.
O'Callahan's major breakthrough as an adult storyteller was "The Herring Shed", which depicts the World War II homefront through the perceptions of a young woman working at a fish packing plant in the Canadian Maritimes.
They nevertheless deal in this microcosm with larger historical and cultural issues including class and ethnic prejudice, politics, the effects of alcohol abuse on family members, the plight of Japanese-Americans during and after World War II, and the complex nature of heroism.
O'Callahan has created other long-form adult stories from factual material, always from the intimate point of view of a central narrative character, and imbued with a sense of the mythic.
These include "The Spirit of the Great Auk" a tale of Dick Wheeler's real-life epic kayak trip along the eastern coast of Canada and New England, following the migratory route of the extinct great auk, and encountering its ghostly spirit; "Pouring the Sun", commissioned by Bethlehem, Pennsylvania to commemorate the city's steel-making history; and "Father Joe: A Hero's Journey" the story of his uncle, U.S. Navy chaplain Joseph T. O'Callahan, who saved the USS Franklin (CV-13) after it was set ablaze by Japanese aircraft during World War II.