Just dropping round bales in front of them you need to ensure there is plenty to go around, but more importantly - room for them all to eat at once. If you're limiting how much they get per feeding, some cows will always eat more, either because some push to get more than their share, or they just eat faster than others.
Having more than they need in front of them at all times ensures there's always some there for the wimps of the bunch. And I'm not talking the feeders are still full the next day when you show up, but if it lasts for day light hours more or less, than everyone has had multiple turns at it.
Even in a tie stall barn its hard to limit, because they can steal off their neighbours.