"Overland trout” is a cowboy slang name for “bacon.” The term “overland trout” was part of a larger cowboy slang list that was printed in many newspapers in 1887.
24 February 1887, Belmont Chronicle (St. Clairsville, OH), pg. 1, col. 4:
The cowboys have a language of their own which no “tenderfoot” may attain unto until he has served his novitiate. (...) Bacon is “overland trout,” and unbranded cattle are “mavericks.”
(This story appears to have originated in the Omaha Daily World, February 1, 1887, og. 2, col. 5—ed.)
Google News Archive
10 March 1887, St. Joseph (MO) Weekly Gazette, pg. 11, col. 5:
THE cowboys have a language intelligible only to the initiated. (...) Bacon is “overland trout,” and unbranded cattle are “mavericks.”
A Dictionary of Slang, Jargon & Cant, Vol. II L-Z
Edited by Albert Barrère, Charles Godfrey Leland
The Ballantyne Press
Overland trout (American cowboys), bacon.
A Room for the Night:
Hotels of the Old West
By Richard A. Van Orman
Bloomington, IN: Indiana University Press
... and the four B’s — sourdough biscuits, bacon (called by cowboys “overland trout"), beef, and beans.
By William H. Forbis
New York, NY: Time-Life Books
Over his fire cook Garcia boiled the beans that were his monotonous specialty — “Pecos strawberries,” the boys called them. For meat Garcia almost always served fried bacon, or “overland trout.”
By Catherine Creel
New York, NY: Kensington Pub. Corp.
Dusk had fallen by the time everyone had finished a supper of fried bacon, called “overland trout” by a few of the drovers, pinto beans, boiled potatoes, and sourdough biscuits.
The Cowboy Encyclopedia
By Richard W. Slatta
Santa Barbara, CA: ABC-CLIO
Colloquial term for bacon.
September 28, 2012 - 12:46pm
27 Cowboy Slang Terms for Things You Eat and Drink
by Adrienne Crezo
2. Overland trout: Bacon