Chances are that if a cottontail rabbit can eat something, our domestic bunnehs can eat it, too. Here are some foraging choices for your rabbit masters, and perhaps a couple for you as well!
The Common Dandelion
Did you know that cottontails even eat poison ivy? I do NOT encourage harvesting this nommable. Rabbits also love the bark of some trees, seeds, flowers, and nuts. I have a paper-shell pecan tree in my yard, and for a treat, I like to sprinkle some pecan halves into their breakfast or supper now and again.
Definitely be careful when wild-harvesting for you and your bunnies. Stick with easily identifiable herbs, grasses, and plants.
Remember that rabbits love the seed heads of grasses! And nearly all wild grasses are edible for rabbits. Some are tender and juicy, some are rough, and some are just plain strange looking, like they shot out of the ground as hay already.
Happy (and above all SAFE) harvesting!!