It sounds like from your other post that your bunny is still fairly young.
Bunnies can start to be introduced to veggies one at a time in small quantities starting at about 3 months - about 1/2 ounce of veggies per day.
At about seven months you'll start to slowly increase his veggies. Once he's about a year - increase it to about 2 cups a day of fresh dark green veggies per 6 pounds of bunny.
Dark green veggies tend to have the most nutrients. Herbs like parsley, dill and basil are big hits around my house. Carrots are a treat, so should be given sparingly.
Here's a list of good veggies for bunnies - you'll want to add them one at a time to see if your bunny has any adverse reactions to them. Over time it's good to offer your bunny a variety each day. I find a lot of bunnies will turn up their nose at things the first time and then later love them - so you might try new things more than once.