Glad the suggestion helped. I'm sorta doing the same thing for my chickens this year; my garden is a few hundred feet away and up a hill, so having some goods nearby their run will be handy.
I planted some cover crop in Fall that grew against the fence and they enjoyed pecking at that...
I'd likely plant some fast-growing veggies with leafy greens that could be quickly harvested and fed to them. Something easy to sow or self-sowing - radishes, peas, leafy greens, herbs, etc. Could even be something perennial - such as tree collards, my chickens love eating tree collards