Harper was active in the ​Indigenous rights movement of the 1970s. During this time, he served as vice-president of the ​Ontario ​Métis and Non-Status ​Indian Association (1972-74). With his wife Pauline Shirt Harper, he organized the Native People's Caravan, a cross-Canada trek ending in a lengthy encampment in ​Ottawa (1974-75) which succeeded in bringing together Indigenous organizations to publicize their grievances. The ideology of the demonstration had strong traditionalist and spiritual elements which reappeared in the Wandering Spirit Survival School of ​Toronto, founded by Pauline and Vernon Harper in 1976. He is author of Following the Red Path: The Native Peoples' Caravan, 1974 (1979).