Intervention Beta was held 26-28 September 1980 in the Ramada Inn, Salt Lake City, Utah.
A listing for the convention in Starlog magazine #38, September 1980, page 70:
Flier for the convention, courtesy of Michael C. Goodwin:
Program book cover, courtesy of Michael C. Goodwin:
An article from the Deseret News dated 27 September 1980, page B3: