From Yellowstone to Eugene, OR

Out of Bend another option is to take the Cascade Lakes Scenic Bypass past Mt Bachelor and a number of lakes and lava beds (and campgrounds). At the south end it connects with OR58 which is another good route to Eugene. Willamette pass is barely noticeable when coming from the east. Be sure to check the Salt Creek waterfall.

Personally I would take Hwy 26 in from I -84 but that is so I could stop at John Day to visit the Kam Wah Chung Museum and the fossil beds again. I've been twice and except for my encounter with a rattle snake at the fossil beds, I would do it a third time. Hwy 26 was find all the way across Oregon. Couple of pulls but nothing exciting.
On the other hand if you take Hwy 20, you will be sooooo close to Crater Lake and a stop just for a couple hours is really worth the extra time.

You do need to be aware that the Sisters Outdoor Quilt Show is the second Saturday in July, if that is your timeframe. There will be NO available space at the campgrounds in and near town. You can, however, usually find something out toward Camp Sherman or at Suttle Lake.

If you take Highway 20, there is a great county campground (River Bend) shortly before you get to Sweet Home. Very nice, private sites, clean restrooms and showers and easy on and off of Highway 20.

Also on that highway, if you see a sign that says "sunken grade", slow WAAAAY down.

2gypsies wrote:
From Boise we've taken both 20 and 26 and enjoy 26 better for the drive and scenery. They're both o.k. for RVs though.

When you get into Sisters definitely stay on 126 into Eugene. Don't be tempted to take 242 to 126. You won't like it in the RV. Steep. 126 into Eugene is a pretty drive following the river.

Gypsies is correct.

26 is a bit steeper and curvier, but far more scenic.

DO NOT take 242 out of Sisters. 35ft max total length.

Coming down the pass after Sister; take it easy. It's a long ways down. After the second left onto 126; there is another pretty steep downhill run also.

There is a city RV park in Sisters and Sisters is a nice place to visit.
ParkCrown Villa RV in Bend is a very nice park.

From Boise we've taken both 20 and 26 and enjoy 26 better for the drive and scenery. They're both o.k. for RVs though.

When you get into Sisters definitely stay on 126 into Eugene. Don't be tempted to take 242 to 126. You won't like it in the RV. Steep. 126 into Eugene is a pretty drive following the river.

Sorry I can't help with the last part of your route, but the rest of it should be fine. If you'd rather pick something more scenic than the Snake River Plain, you might consider US 20 across Idaho instead of the interstates.

road is fine just run on top half and remember this route is high dessert. hot hot and sage brush.i-84 to 205 to i-5 to eugene will be quicker but is freeway all the way.if you haven't seen the columbia gorge it might be a consideration

Have driven the 126 but don't remember it; should be ok. The rest, in my mind, is great. I have driven it several times with the 5er.