Here is our Guide to The Best Foods For Rabbits! We discuss what foods are best for rabbits and what are not good for, or may kill, a rabbit.
It links with several informative articles on Hobby Farm Heaven.

No, rabbits and bunnies should not eat corn. Corn is not part of a rabbit’s primary diet and is generally too sweet for rabbits.

Can Rabbits Eat Beets? Yes, in moderation adult rabbits can eat beets. The fresher the better!

Can Rabbits Eat Zucchini? Yes, adult rabbits may eat zucchini, in moderation. It is a unique fruit in that it is not high in sugar.

Yes, adult rabbits may eat a small amout of grapes as a treat, not as part of their primary diet.