Bone in leg of lamb

they cook fast at 350/400 (i go 400). say 90 minutes or so. i go to about 140 in the thickest part of the leg. the nature of the leg, with thick and thin parts, means you'll have well done and medium-rare to medium for the squeamish types.

i go at 400 to get a nice crust (rosemary, salt, pepper, garlic slices tipped into the meat, or garlic powder), and the short cook means i still have plenty of rare meat. put it on cold...

true "slow roasting" would be around 250, and i don't know how long you'd go. i think a crust is attainable at those temps, but am not sure. they do it with prime rib... i would hesitate to try searing direct combined with roasting (either before or after), because lamb has a nice amount of fat, and it tends to get bitter when seared. but you could go very slow indirect (monitor meat temps!), and then crank the dome to 500 for fifteen minutes at the end when you hit maybe 120 internal, to finish it.

i think you will get a lot of different answers on this. i sear the leg in a hole directly in the red lump then rest it til the temps are down to 325 dome and then roast. i pull the leg off at 122 to 125 internal. i cook them at a lower temp because i want that lamb to be red across the middle (and cooked closer to the bone) and charred on the exterior. lamb fat is not good, cut it all off before cooking, especially if you want this more done. lamb also takes a marinade nicely. i make up a tabouleh salad and make extra dressing to marinade the lamb in sometimes.