I wear glasses under my goggles, and last season I tried just about every kind of goggle to find what works the best for me. Helmet had a lot to do with it as well.
I started off with a cheapo fly helmet and some scott xi goggles, and I was having a terrible time keeping my glasses from being fogged up.
I tried a set of oakleys - no better. What were better were 609 sinisters, and they fit my glasses just as good as the scott OTG glasses.
The biggest change I noticed was changing that cheap fly helmet (kinetic I think it was) for a klim f4. The extra venting did help A LOT with keeping the glasses from being fogged up under the goggles.
I also got new glasses mid-season last year, and got a new coating called opti-fog on my lenses. The coating is made by crizal, the same company that does the anti reflective coatings. I rub on some of the opti-fog activator before going (which lasts about a week or so), and those glasses were near impossible to get foggy after that.
I am going to try to get some contacts before this season starts, but after getting the opti-fog coating I have no trouble wearing glasses and worrying about them being fogged up, regardless of the helmet and goggles.