Are you vegetarian or vegan? Are you a lacto-ovo vegetarian?
My advice is kind geared toward lacto-ovo vegetarians...but I am sure that if you talk to the chefs at the restaurants, they would find vegan-friendly entrees. (and I am highlighting the fare that I enjoyed, b/c I am sure that if you are like me, you like salads, but not as the main course for EVERY meal).
At TS, if you pick the buffets (in the parks: Crystal Palace, Hollywood and Vine), they have LOTS of offerings that were vegetarian-friendly. (sundried tomato risotto, for example.
Tapan Edo in Japan (Epcot) is another great option for getting your weight in grilled vegetables, rice, and udon noodles (with the cute Hibachi presentation as well).
Another would be Chip and Dale's Garden Grille for lunch (living with land Epcot)...they have super fresh vegetables, and I am sure that the chef can come up with an offering for you all.
Restaurant Marrakesh in Epcot has vegetarian options (like the vegetable kebabs on a bed of couscous).
Wolfgang Puck at DTD has amazing ravioli (pumpkin and 3 cheese varieties).
I know that they have vegan offerings at Boma (but I am not sure if that is all of the time, or my special request/reservations).
You could call the special dietary needs hotline at 407-824-5967 or emailing them at
SpecialDiets@DisneyWorld.com.
Most places, talking with the chef about your lifestyle preference can help too. Sometimes they have a tofu that they can sub in for your entree (but not always).
As far as QS, I would suggest:
Sunshine Seasons at Epcot
Harbour House at MK (but you have to modify the HUGE salads to not have the chicken or fish on top) or Pinnochio's Village Haus.
At AK, eating a pizza at Pizzafari or fruit from the fruit cart in Kindani Village (sp?) or french fries at the burger places. When we went to AK, my sister and I would eat a huge breakfast and then snack on the fresh fruit or take a boiled egg into the park for a light lunch...AK was always hard for me where meals were concerned.
At Hollywood Studios, I really liked the Tabouli offering at ABC commissary.
At DTD, I would pick Wolfgang Puck Express...they have an amazing spinach salad and a Mediterranean foccacia melt that was AMAZING.
Good luck and bon appetit!
PS There are probably stickies on this subject too, but I figured that I was just posting up my faves amongst the veggie fare.