I've never had a problem with grass but I wouldnot suggest any veggies. I know that2 of mybunnieswould eat all of it and not stop and could end upsick. It's possible that could happen. Grass should be ok because it'snot really rich. My bunnies get all the grass they want all summer andspring/fall if weather permits.
It's up to you but I would highly suggest just feeding a limited amountof veggies once a day. On top of that, they may stop eating pellets/hayif they have access to that. They may get picky and only want veggies.It's happened to me!
EDIT: In response to FreddysMom's post, grass is only safe that's notsprayed or fertilized! My dad does not get any where near the runs withand kind of chemical so that the grass is safe for them. NEVER feedgrass that may have chemicals on it!