That depends on the vegetable.
Hard veggies like carrots and celery can be cut in advance. They do best if stored in water once cut.
Cutting onions in advance can be done, but you will lose a lot of the bite of the onion. For green onions, it's not as pronounced, so they can be cut a couple days ahead usually.
Potatoes can be cut in advance, but you have to store them in water or they'll turn gray.
Softer veggies like peppers, eggplant, tomato, cucumber, don't really do well cut in advance. Peppers, tomato and cucumber can stand being cut a day ahead, usually, but not much more than that, depending on what you're doing with them. They will all get softer the longer they sit cut. Store them well wrapped. Eggplant needs to be cut right before cooking, it will oxidize on cut surfaces, and it cannot be soaked since it acts like a sponge.
Mushrooms can be cut in advance, kept well wrapped.
If you have a specific veggie you're thinking of that I didn't list, be sure to ask, but I think I covered the basics.
Cristeen ~ Always remembering our warrior ~ Our is 3, how'd that happen?!?!
We welcomed another warrior in May 2012!!
2012 Decluttering challenge - 575/2012