Just did my first one of these for BOS. I was to go to Oberland station and "secure" crops to feed fellow BOS member's. I've succeeded but now they settlement is owned by BOS and not Minute Men. Is there anyway you can make the NPC that gave you the quest happy without completely handing over the settlement to BOS.
Edit: I even attempted to buy the crops off of the NPC that owns the settlement. Once haggled her down to 500 caps, it still said "Oberland station is no longer allied to you."