The most common owl nesting in the Tetonia Area is the great-horned owl. They don't use nest boxes; they use stick nests built by hawks and corvids. Tetonia also gets frequent winter irruptions of great gray owls that move down from adjacent National Forest lands to valley cottonwood stands. These birds prey on pocket gophers and voles. Great Grays likely move to lower elevations due to dense snow conditions in the mountains that inhibit hunting. Your best bet for attracting a vole eating raptor to nest in an artificial structure in the Tetonia area may be kestrels. They are abundant and readily occupy suitably constructed and sited nest boxes.
The link below provides some general information on American Kestrels, incluing how to construct and install a nest box. Hope this helps. Best of Luck.
Rob Cavallaro, Regional Wildlife Biologist
Upper Snake Regionional Office, Idaho Falls