IMO they like all seeds. Left to their own devices on pristine pasture they'll scratch for seeds and bugs all day and eat a bit of greens at the same time but seeds and animal protein would make up the bulk of their diet.
In cooler weather I usually feed a blend of wheat, barley and sunflower seeds.
I also sprout or grow fodder from those as well as peas and buckwheat. The buckwheat doesn't seem to be their favorite.
Sunflower seeds have more vitamins than most grains.
In the heat of summer the only grain I give is oat groats.