Grateful Dead, New Riders of the Purple Sage, The Band, Janis Joplin, Delaney & Bonnie, Mashmakhan, James & the Good Brothers, Charlebois, Ian & Sylvia, Buddy Guy, and Tom Rush
Alan Bershaw supplies this facebook post with a photo, video clip, and this tantalizing tidbit, Garcia is "playing a Telecaster previously owned by George Harrison - same one he played on the Apple rooftop gig!". Old TJS notes call it the "Let It Be" Tele.
This was a 2 day festival but the Dead and NRPS only played in the stadium in the 4th, not the 5th.
deadsources: July 4-5, 1970: McMahon Stadium, Calgary (Festival... — John Gibbs (Calgary Herald, 3 July 1970); unknown (Calgary Herald, 3 July 1970); unknown (Brandon Sun (Manitoba), 4 July 1970); Catherine Campbell (Calgary Herald, 3 July 1970); Jacques Hamilton & Catherine Campbell (Calgary Herald, 4 July 1970); Bill Musselwhite (Calgary Herald, 6 July 1970); Catherine Campbell (Calgary Herald, 6 July 1970); John Cosway (Richmond Review (Richmond, BC), 10 July 1970); unknown (Cash Box, 25 July 1970)