The Food Lab: The Best Way To Grill Sausages
May 30, 2012, J. Kenji López-Alt, http://www.seriouseats.com/ (brief summary)

Hot Dogs in Sauerkraut and Whole Grain Mustard
Hot Dogs in Sauerkraut

What Not to Do

Just like other meats, sausages contract as they cook, and in proportion to how hot they are cooked to. Cook a sausage over high heat, and the casing and the outer layers will quickly get very hot, causing them to contract a great deal. Meanwhile, the raw sausage meat in the center has not contracted at all. What happens next is the casing and outer layers crack and burst open.

Okay, so this time you take it to the opposite extreme, cooking the sausage the entire way through on the cooler side of a grill. You get a tiny bit of browning, no bursting at all, and when you pull it off the heat, it looks plump and juicy as can be, but within moments it deflates like a sad balloon, a wrinkled, dry shell of its former self. What happened: With not enough heat, by the time you get any significant browning on the exterior, the interior layers have already overcooked. Steam and expanded muscle tissue will give the sausage a plump appearance while it's still hot, but as soon as it comes off the grill and cools slightly, it shrivels up again.

The Science of Sausage

That said, the rules of meat cooking still apply to sausages: you do not want to overcook them. The simplest possible solution is to cook the sausage over moderate heat on a grill. I find that by building a two-zone fire with all the coals piled under one side of the cooking grate, I can move my sausages back and forth from cool to hot side, carefully monitoring their internal temperature with a probe thermometer and finagling it so that the internal temperature comes up to 150°F just as the exterior reaches a perfect burnished, crisp, deep brown. Using this method, you can get an evenly cooked sausage with plenty of smoky grilled flavor. It works, but it's not easy.

The second solution is much more foolproof, and the one that's recommended by many grilling experts: Poach them first.

Simmered 'N' Grilled Sausages

By placing the sausages in a disposable aluminum pan (or heavy duty aluminum foil boat) along with a moist, flavorful accopmaniment—say beer, whole grain mustard, sauerkraut, and thyme to go with these bratwurst—you can simmer the sausages directly over the grill, imparting them with flavor from the ingredients in the pan, as well as plenty of smoke from the grill.

I pile up the coals on one side, place the trays on the hot side until the liquid is just barely simmering, transfer it to the cooler side, cover the grill with the vents open over the sausages (to encourage good convection current) then let them slow cook until they reach close to their desired final temperature of 150°F. This takes about 20 minutes or so—plenty of time for the smoke, condiment, and sausage flavors to all mingle.

Only after it's cooked to I transfer it to the hot side of the grill (which by this point is only moderately hot) to char the sausages and give them some snap and color. You may find that even with the par-poaching technique, a minimal amount of ripping will occur on the skin when you transfer it. That's okay. By this point, the interior of the sausage is already cooked and the protein matrix is doing a fine job of holding the fat and other juices in place (provided you didn't overcook it).

There are some more advantages to this method. I've found that once the sausages come to temperature, if you remove the lid of the grill and pile the sausages up as far away from the heat source as possible, they'll stay hot, but won't continue to cook. That means that your sausages are ready when your guests are ready, not the other way around. All you've got to do is grab a sausage, throw it on the hot side, and in a matter of moments, it's ready to serve along with a few scoops of its condiment.

Flavor Variations

Be sure to toast the buns! Modify the recipes for the grill following the technique outlined above.