Shape: Traditionally a meatloaf goes in a loaf pan. We want to make the most of the smoke flavor so we want to expose as much of the surface of the meat as we can. Similarly we want a shape that will maximize our smoke exposure. I keep the basic loaf shape, but without a pan to hold it together, more like a french bread than a store bought white bread. Make sure that you make the loaf as thick through the middle as possible so that you can keep the center moist.
Ingredients: There are hundreds of recipes out there for meatloaf so I'm not going to spend a lot of time on what goes into it right now. What I want to say about your barbecue meatloaf ingredients has more to do with consistency and texture. Considering the shape we want and the fact that we are not going to be using a pan to hold its shape, we want a meat mixture that is firm enough to hold together while the meatloaf cooks. This doesn't mean we want a dry mixture, just a firm one.
Seasoning: Since we are aiming for a barbecue meatloaf we want to treat it like we would other barbecue meats. This means we want to use a good barbecue rub. Of course you are going to be putting flavor into the meat mixture, but what I like to do is dust the surface of the meatloaf with the rub to help give it a flavorful, crusty surface. This gives the meatloaf a texture (soft in the middle, crispy on the outside). So use a rub to flavor the mixture, but also apply it to the outside.
Placement: In most smoker the smoke rises. Placing your meatloaf in a large pan is going to deflect a lot of the smoke away from the meat. We don't want that. One strategy is to place the meatloaf on a wire rack and then put this on the smoker grate. Problem is the meatloaf tends to slip between the grids. Alton Brown suggests using parchment paper cut to the size of the meatloaf. This works perfectly to keep the meatloaf together while letting smoke move around it. This is the method I use.
Temperature: Ground meat should not spend a lot of time at a low and slow temperature, so we are going to turn up the heat on this barbecue dish to around 250 to 275 degrees F. This will still allow the BBQ Meatloaf to cook slowly and get a good dose of smoke, but it will cook it fast enough to keep bacteria from growing. To be safe you must heat your meatloaf to a minimum internal temperature of 165 degrees F.
Smoke: Ground meat absorbs smoke much faster than other meats so we want to keep to small amounts of a mild smoke. Fruit woods work best with meatloaf, particularly apple. Because we don't need a lot a smoke for our BBQ Meatloaf you really don't necessarily need a smoker to make this. Charcoal grills work perfectly and if you can generate smoke on your gas grill you can use that as well. Make a little smoke and you will be good.
Finishing Off: As with any meat you grill or smoke your meatloaf needs some time to rest. This will allow the meat to relax and the moisture to spread out evenly inside. Once you have finished cooking the meatloaf, take it out of the smoker, cover and set aside for about 10 minutes. Then carve and serve.