Regarding beef, my grass-fed beef farmer will harvest his own grass to use as hay in the winter. The guy who processes the cows tells me the farmer has gotten pretty good at managing the grass/hay, and it's hard to tell the difference in meat harvested at different times of the year.

As I understand it, most egg producing chickens, including pastured chickens, are given at least some grain. Whether or not they are organic therefore depends on the feed, not the season. "Free range", as near as I can tell, is nearly meaningless and does not mean the chickens necessarily spend any substantial amount of time outside on pasture, although at the very least it ought to mean they aren't kept in cages all the time.

In the US, you have to check with each beef producer because there are no legal standards, but the farms I buy beef from only give hay in the winter, not grain -- so that is the difference between their beef vs. grain-finished.