You can always ask your servers to check on what is in certain items. If you eat milk and egg products, there are sometimes items on the main menu that you can order, but there are always 2 vegetarian entrees listed each night.
One day for lunch, we ate at Tritons, and they don't list vegetarian entrees at lunch. That day we ended up ordering 3 appetizers instead (our server suggested it as an option, but also offered to have the chef make us something else). Well that worked great! We loved every one of the appetizers and it was one of the best lunches we had the whole time!
I have never done it, but people have mentioned that on the in-room dining menu there is a grilled ham and cheese sandwich, but that you can ask for it to be just a cheese sandwich.
I also noticed at Plutos they now have nachos and salads as well as veggie burgers.
Personally, one of the reasons my family LOVES the
DCL is because, as vegetarians, we feel we can always find something good to eat! Same at WDW. Most of the times on vacation, we have trouble finding something, but Disney does a great job.
DJ