The reasons the answers vary is because they must, as there are so many variables.
If your birds were battery birds, with constants of temperature, they'd be fed 4 or 5 ounces of complete layer formula, per day, everyday.
Since your birds range, it is going to vary, based upon how successful their hunting was that day. How lush the grass was, when it rained last, which insect was "in bloom" that particular day. In winter, an animal eats more simply because the range is typically dead and increased calories are required for body heat generation.
Start out the day feeding them a healthy portion, 3 oz each bird, of complete ration. If layers, then layer formula. When they return to the coop in the evening, offer then an additional feeding of 2 ounces per bird. If they show little interest in the evening feeding, you can reduce the morning feeding amount. It is a balancing act, that requires observation of how much feed they are requiring. Watch the feeding troughs. If they are emptied quickly and often, you'll have to up the portion. If they troughs are often have full? You can reduce the amount fed and reduce waste and rodent attraction. The birds themselves determine whether they are requiring 4 ounces or 6 ounces per day.
Finally, different breeds have differing feed amount requirements. Some birds are more thrifty and are better at feed conversion.
In short? There are no simple, one size fits all answers.