Ok, I'll go.
Experiment one: Late last summer. Unsuccessful.
I picked out a bag of cheap birdseed made up mostly of millet and milo and canary grass seed. I had a patch of dirt in the back yard where I had cleared ivy from, so I broke up the soil and scattered the seed and raked it in.
Results: The chickens took them about an hour to find it and start digging up the seed and eating it. I put up some fencing to keep them out. The squirrels, chipmunks and sparrows finished off the rest of it.
Experiment two: Late summer/early fall. Mildly successful.
In my fenced in garden, I planted a sort of cover crop among the tomatoes. In one area I mixed winter rye with crimson clover. In another area I mixed oats with white clover. In another area I mixed some of the leftover birdseed from experiment one with white clover.
Results: I got a lot of seedlings throughout all areas. It was very popular with the local wildlife. Once it was clear nothing was going to make it to full growth, I started letting the chickens in for supervised foraging time. They seemed to enjoy picking through the remaining growth almost as much as digging for worms in the mulched paths. The birdseed and clover area was the only area with green left when frost hit. Patches of clover (and a little bit of mystery plant) survived through the occassional foraging over the winter. There is a tiny bit of clover that is still growing there.
Experiment three: Early spring. Still ongoing.
I built a 4 four foot square frame from decking material that was on sale. I stretched chicken wire over the top. I covered that with bird netting. I planted the bare patch from experiment one with a mixture of naked oats, crimson clover, and a couple rows of field peas. I covered the patch with my frame (chicken wire side up.) My plan was that the chickens could graze off the tops of the plants without digging them out of the ground.
Results so far: As the seedlings started coming up, the chickens started studying. After a while, they figured out that they could stand on the wire and make it sink to the ground in the middle so they could pick the seedlings out. Ok, fine. Let them have the middle. Then as the oats started growing taller, I noticed the chickens would get hold of the end of a blade of oats, give it a yank, and pull the whole plant out of the ground and eat it. I fenced the chickens out. So far, the growth is about 4 inches tall and poking through the netting, and the local wildlife is leaving it mostly alone.
Meanwhile, I know this isn't forage, but I got out my sprouting jar and sprouted the birdseed from experiment one in small batches over the winter. The girls go NUTS over it. They like it better than BOSS.