Hiya DLT,
You'll hear many people say lamb is best done hot and fast on a grill. I agree that it's great that way, but I don't agree that it's not a candidate for cooking in a smoker. I get great results doing lamb and I always have some in my freezer.
I use this recipe on lambs roasts and chops and I think it's good. The steps are:
1. Marinate
2. Sear
3. Smoke in a preheated smoker
Marinade
4 large shallots
4 cloves garlic
2 T rosemary
1 serrano pepper, seeded
3/4 C olive oil
2 t cracked black pepper
1 t juniper berries
1 T spice rub
1 t salt
1 T orange zest
juice of 1/2 orange
Stick all the ingredients into a food processor and whizz it up. I use a morter and pestle but an FP works just fine. Cover the meat with the marinade and let it sit at least two hours, preferably overnight.
Remove the meat from the marinade and sear it on a very hot grill or cast iron pan.
Preheat your smoker to the highest possible temperature. I get mine up to about 250 F with full smoke. Put in the meat and cook it until it's just medium rare. I like about 130 - 135 F internal, but this will vary by taste and by the cut of meat (large roasts should come out a little earlier because of temperature overshoot).
If you want you can also use a dry rub. Here's one I use for lamb. You can substitute or leave out any of the hard to find ingredients, like smoked tomatoes. Don't worry about that part of it, just have fun and experiment a little.
You can make your own smoked tomato powder from this recipe with your smoker but I'll leave that to another discussion.
Good luck!
Lamb Rub
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Qty Unit Ingredient
0.25 C Paprika
0.25 C Garlic Powder
5.00 t Onion Powder
1.00 T Salt
1.00 T Black Pepper
1.00 T Cane sugar
1.00 T Sage
1.00 T Thyme
1.00 T Smoked Tomato
1.00 T Guajillo Chile
1.00 T Pasilla Chile
1.00 t Cumin
1.00 t Ginger
1.00 t Clove
1.00 t Caraway
0.50 t Juniper