Spooler, how many mares and how many geldings?  How big is your pasture?  Who is causing the problems?  (I'm guessing its the mares but here at my place, its my gelding that stirs everything up so thought I'd ask)

If its one horse in particular starting trouble (i.e. dominant mare), try just taking that horse out of the mix for a bit and see if everyone else can't figure out how to get along......then reintroduce the instigator to the herd.  That seems to work best for me. 

I keep all my horses together with little problem.  I find that this time of year is the worst for everyone.  They are happy and ready to play.  The mares are starting to come into heat and think the geldings are a joke.  I just let them work it all out.  If one is realy badjered I will remove for a few days but they always go back.  I seam to have a very happy heard of horses and I am able to inturduce new horses fairly easaly.  Horses just want to know who is boss and wheir they stand.  Good luck

 Normally it is not a problem but the 2 mares are of coarse in season.  The dominate mare is not and believe me  NO Horse gets near her unless she gives it her O.K. The 2 geldings came back to where I was begging to be put up. They just had that look.  Pointed toward their paddock gate and was met their. Open the gate and in they went. Of coarse it is my horse that is starting all the trouble(mare).  She runs on 103 Octane. The other 4 are the wife's. So 3 mares and 2 geldings. She is the youngest of the heard. She will be 4 in July. The other day was a beating fest for sure. Poor fellows, I feel their pain.

They are let out on 5 acres of pasture once a week until the pasture gets growing. PMS sucks!!!! Figured that is what it was just wanted to be sure.

I've got two mares and two geldings all in a 1/2 acre paddock.  They share the same run in shed. I put their hay out in two mangers (about 100 feet apart)  They've all been together for about 4 years.

The geldings are the boss around here.  My 12 year old Arab still acts kinda like a stud and chases everybody away until he figures out which manager he wants to eat out of.  Or until he gets all the attention he can stand from anybody offering to scratch or brush him. He always herds everybody around. The mares head for the other manager.  My second (younger) gelding is the 2nd in command and take choice of where he wants to eat.

The only time my mare will stand up for herself is when she has a new foal.  So I have to seperate her for a couple months when the babies come.

It's the same when I go for a trail ride. The geldings are my leaders. The mares just follow nose to tail. So i think it all depends on the personality of your herd.