I'll be spending 2-3 days during the first week of September in the Willamette Valley (staying at Youngberg Hill). I'm looking for recommendations on which wineries would be 'best' to visit and why, and where would be great places for a picnic lunch. I'm also interested in any wineries that are less commercialized -- even if it means we might need to arrange in advance for a private tasting/tour as a way to get a better feel for the winery and its wine. Any other thoughts on this area would also be appreciated.

We really like the Sokol Blosser winery, not only for the quality of their wine, but also for the warm welcome they give visitors and their environmentally friendly approach to winemaking. We met Susan Sokol Blosser, one of the owners, a few times at wine tastings in NW Portland, which sparked our interest in visiting the winery. Check www.sokolblosser.com to see if it's for you.

Sorry to not be able to help since this is my neighborhood but I haven't done the winery thing. My guess is that the wineries in Oregon are less commercialized than elsewhere. Of course some of the bigger ones (Willamette Valley Vineyards) are fancier and have put more money into visitor areas but some others I have been to (for wedding or driving by) are much more casual.

Here are two websites I found, hope they are helpful. oregonwine.org, winesnw.com

Enjoy! Oregon in Sept is beautiful!

Don't know where Youngberg Hill is, so I don't know which places would be closest to you. But Rex Hill is easily accessible off the 99w,has great wine and the grounds would make a nice area for picnics. Dundee Springs is a small place also on 99W and has nice wines that you'll not find elsewhere, I don't think. There are so many options!
My suggestion is to call The Oregonian and ask for their back copy desk (503 221 8242) Every Memorial Day weekend the wineries are all open and have special events. The Oregonian puts out a winery guide. While the events and hours of opening would be mostly inaccurate, it will list the wineries by area and have maps. I don't recall the price of a back issue but it's so cheap to have them mail you a copy, you should consider it.

I live in the Willamette Valley and have done three wine touring excursions around here and I'm going on a fourth Labor Day weekend. I like Eola Hills, Willamette Valley Vineyards (more commercialized, but I've done their winery tour twice and enjoyed it both times), Cristom (beautiful tasting room), and Witness Tree. Frommers.com has a guide to Willamette Valley wineries and there are directions to all of these wineries in there. The only one I don't recommend is the Ponzi tasting room and restaurant. I haven't been to the Ponzi winery near Beaverton, but the Ponzi restaurant is located away from the winery and I found it mediocre and overpriced. You can do tastings there, but what we tasted on the day we arrived wasn't that great and they didn't have a very good selection. I'm going to visit the winery at some point. St. Innocent's wines are good but their tasting room is tiny and not much to brag about. However, it is almost never crowded, so you have a chance to talk to the server about the different wines. St. Innocent's winery is small and does not do tours.

Nothing to do with wine, but the Evergreen Aviation Museum with the Spruce Goose is not far from Youngberg Hill (although not very well marked). It's worth a stop if you've never been.

I would definitely not miss the Willamette Valley winery. The Pinot Gris is excellent. You can take your tastings out to the patio and enjoy the beautiful views of the vineyards.