The birds are free ranging.
What do you feed in addition normally?
What do you think they are getting off the pastures?
How many birds?
Sun Dried Grass Clippings can be stored.
In winter in snowy conditions Grit is a must.
I watched a video on how an organic farm through a sequence of events went from grain feeding with free ranging, to free ranging with compost piles becoming the food for all their birds no grain year round. However you need to develop a system, have free access to food scraps and waist of restaurants, a community that wants to reduce landfill… they also buy quality additional materials for their compost formula. All the food waste has to be ground up then added to specific created piles… also they are not trying to maximise growth or eggs per say. They are however creating top quality compost for their farm and to sell, they do sell the eggs and are working to expand it. So a well run compost pile system might help supplement… but you need to set it up right. The guy said he figured each hen used 2 lbs of scraps a day, other folks he said felt it was closer to 3 lbs (apparently others have recreated their accidental feed alternative, they did not set out to feed the birds this way). He had 600 birds being fed that way, but they could feed up to 1200… 600 birds gave them roughly 300 eggs per day… they were in process of culling and adjusting flock breeding towards egg production so had already culled about half the flock. You need to be realistic with this sort of thing, work, runoff control, understanding how to do it… and costs of needed materials. I have not tried this at all, just watch a video interview on how that farm operates… they have staff and equipment and it is a pretty big to do.
I am not sure how many bugs and worms you would need to raise to feed your flock in winter.
What is your storage space? How much feed do you normally feed them in winter?
What are you buying at the grocery store?