Pork loin is one of my fav's to cook. I suggest getting some heavy duty alm foil and wrap it. Put some butter in the wrap along with some hendrixsons salad dressing. http://www.hendricksons.com/
Take the wrapped loin and put on a broiler oven tray and cook to temp. Before you take it out of the oven start up a charcoal grill. Move the loin fromt he oven to the grill and unwrap on the grill (will be messy). After you unwrap it..... sear the loin (make sure the grill is nice and hot. Sear the loin all around and then cut and serve with Beirnaise sauce.
You will be loved by all of your party guests.... unless you want to retain it all for yourself.
I plan on bringing some of this dressing with me and preparing some fish with it. I have used italian dressing in the past but this stuff takes the cake. I will post up and let you guys know how it turns out. http://www.hendricksons.com/