I'm gonna guess that you are asking about the Hoop Dee Do.
The menu is family style.
It has salad, bread and butter, mashed potato, and baked beans (don't know if they are veggie), and strawberry shortcake.
So, basically you have the side items.
You certainly can call the disney reservation line and let them know you would like a vegetarian entree.
According to the menu and info listed on allears.net, they want 48 hours notice for a special request.