I'll assume since you said it's large, it's a warm season grass. While I have successfully moved them in the summer, and theoretically you can do it any time the foliage is 18" tall or less, I'd suggest waiting until next spring. Transplanting a large grass during the heat of summer is extremely stressful to both the plant and the gardener.

If you must move it now, it is best to cut back the foliage by about half. I know it'll look awful, but it will reduce the stress of transplanting. If it's as hot up there as it is down here right now, be sure to dig the new hole first, so you can move the rootball directly into it. Soak the new hole thoroughly, and soak the backfill soil as you are filling in around the rootball. Wait an hour, and water it again. For the first few days, lacking rain, you should water it a couple of times a day.