How cold do your winters get? You're right, a lot of the various greens do well in cool weather and are really good for the chickens. Although my chickens think chard is a fantastic summertime food, too! They recently ate all mine down to the ground. Then they took a dust bath where it used to grow, after digging up the roots. Bad girls...
Kale and parsley grow well into the colder weather. I've harvested parsley that I've had to dig out of the snow. It's the last thing to die off in my herb bed.
Turnips, beets and carrots would be good late in the year. They take cool weather and have a short season. Winter squash is a fall harvest and a good keeper, although for me it has to go in sooner that this.