After gaining climbing experience on the Alps, the Caucasus and the Himalaya, in 1897 Collie joined the Appalachian Club upon the invitation of Charles Fay, and spent the summer climbing in the Canadian Rockies. From 1898 to 1911, Collie visited the Canadian Rockies five more times, accomplishing twenty-one first ascents and naming more than thirty peaks. He was particularly interested in locating and climbing the mythical giants of Hooker and Brown which had bordered the forgotten fur trade route through the Rockies and were reputed to be over 16,000 feet high. In 1903, Collie and Hugh Stutfield published an authoritative book on the region, "Climbs and Explorations in the Canadian Rockies".