I found a good list of cold-weather crops to try next year. To credit the source, here is a link to the University of Missouri article on winter greenhouse growing.
Leafy greens Vegetables Flowers
Arugula Beet Calendula
Chard Bok choi Johnny jump-up
Cilantro Broccoli Linaria (Toadflax)
Collards Broccoli raab Pansy
Cornsalad (Mache) Cabbage
Lettuce Pak choi
I have already proven lettuce production in cool weather, but now that night temps are at freezing or below, crops are growing very slowly. Since I am still in construction mode, I am not set up for a good attempt at winter growing, but my pots are doing OK.