I buy a variety of bulk grains at the local food co-op and share them with our birds most mornings. They seem to be entertained by scratching at and eating any millet, amaranth, quinoa, red wheat berries, BOSS, flax seeds, steel-cut oats, and whatever else I throw their way - all uncooked. Right now, they're just waiting for the snow to melt off so they can get back up to their chicken antics.
Worms can pass on parasites, but I figure every other organism they get their beaks on can as well (for example, slugs).