The common grain can be found in areas of disturbed soils and in grazing fields. Although not the true barley, the grain collected from these seed heads can be used much the same as other grains and was most commonly collected and ground for flour when better alternative grains were unavailable. Collect seed heads when they start to turn golden, and then dry.
Then once completely dried, remove the chaff by beating the seed heads (in which the seeds will fall) or by agitating and rubbing the seed heads. Once the bulk of the grain is removed, in order to remove the finer chaff, you can winnow the seeds by using a gentle breeze to blow away the chaff, or by submerging the grain in a bucket of clean water, where the chaff will rise and can be removed leaving the grain at the bottom to be collected, dried and used in soups or stews or ground into wholemeal flour.