Grosvenor developed an interest in photography at an early age. When was 11, a photograph he took at the Seattle World's Fair was published in the September, 1962 issue of "National Geographic". Grosvenor subsequently worked as a freelance photographer, completing 23 assignments for the magazine and its book division in such countries as Belize, France, Iceland, Spain, Tonga, and Turkey. On several assignments, he was the photographer for articles written by his father on sailing in Canada, Saint Pierre and Miquelon, and the Aegean and Ionian Islands in Greece, which were "thoroughly and ably documented with photographs by [Edwin Grosvenor], the clan’s newest photographic talent," according to Bob Poole in his history of the "National Geographic".