Mine also eat zucchini, peas, corn right off the cob, tomatoes (they loved it when I made tomato sauce and gave them the seeds and skins, they picked through it and ate every last seed they could scratch up), I have planted grass for them (even in the winter I planted some in trays in the basement and took them out to the coop as a treat) but I have thought about grapes growing up and over the run. But then again, I pulled weeds out of the garden and put them in the run and they ate them too, so pretty much anything works for the chickens, it just depends on how much work you want to do. Every gardener has a little extra something to give to the livestock.