The Gallatin River is fishing well right now, especially further in the canyon towards Big Sky. If you're looking for some big dry fly eats, make sure to have some foam in your box. If you're planing to fish the Gallatin make sure to have some Terrestrials, Perdigons, Worms, and Leeches.
Dry Fly
Parawulf Adams (14-22), Purple Haze (16-20), Sparkle Dun (16-22), Elk Hair Caddis (14-18), Stubby Chubby (14-18), Larimer's Yellow Sally (12-16)
Streamer
Woolly Bugger Olive/Black (6-12), Sculpzilla Tan/Black/Olive (4-8), Beldar Brown/Black/Olive (6-8), GD P/Jig Streamer (10), Zirdle Bug Tan (6-12), Urchin Bugger (4)
Nymph
Pat’s Rubber Legs (6-10), Hell Razor Leech (12), Hare’s Ear (16-20), Black Blowtorch (12-18), Juju Baetis (18-20), Worms, Eggs