The Big Country route in southeast Oregon is rated a 9 out of 10 difficulty level, primarily because of some extremely remote sections that would make having a mechanical or injury very difficult to manage. That rating seemed pretty accurate, especially since parts of the route cover mile after mile of remote road that reportedly turn to unrideable muck after rain.
You need to be in shape to ride and/or push 30-70 mile days, depending on how long you take to do the trip, on a loaded bike with lots of climbing. You also need to be completely self-reliant, carrying tools, several days of extra food, and a large water capacity.
If I ride this route again, I will find another more interesting way to skip the Sheldon NWR section. Relentless wind was our nemesis and slowed us down enough that we ended up taking a day longer to finish.
To better your chances of completing the ride, make sure your bikes are in great shape and well maintained, as a mechanical you can’t fix on the trail will send you home early.
Finally, to really enjoy this amazingly beautiful place, take your time and budget a few layover days for hikes, hot spring soaks, and exploring the sites along the way. To plan a safe trip, do your research at Bikepacking.com and other online sources.