If my gals can't go out for some reason (usually I let them out 2-6 hours/day in the orchard, but not if i'm planting or whatever...) I stick big kale leaves through the wire of their run and they go nutso.
Just today I planted a "garden" for them in a wooden fish box I found at the recylce section of the dump. I took this wooden box with slats, about 3ft x 2 ft wide and 8 inches deep and made basically a raised bed with fall greens: chard, kale, lettuces, spinach....covered it with wire on top (make sure to leave about a 2" space between the top of the dirt and the wire covering) and will water it well until our rains start again. When I can't let the gals out for the day this Fall, I'll just roll their new greens garden into their run! (I bought wheels at Home Depot and put them on the end of the box opposite the pull rope.) Voila! Easy chicken happiness!! And with (any kind of) wire across the top (i'm using old horse fencing, but would use poultry wire if i had any more!), they can't scratch all the way into the dirt, so the plants don't mind a little pecking and will just keep growing!!
One idea, anyway...!