Changing a recipe to cook a boneless leg of lamb instead of bone-in.

I am going to be making a recipe that calls for a 6 - 7 lb. bone-in leg of lamb. It was wonderful when I made it with a bone-in lamb. This time I ended up buying a smaller(about 4+ lb.), boneless leg of lamb instead. I am not sure how to adapt the recipe, which calls for an initial 20 minutes at 450, and then another 1 to 1 1/4 hrs. at 350 for medium rare. Should I keep the initial 450, and then cut down the baking time at 350? Thanks for any ideas you may have. And, Happy Holidays everyone!

bella s.f.
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9 Comments

socalfoodie
socalfoodie September 2, 2017
Amanda is right bone in lamb in cooks faster than boneless. But you cook a 6 lb boneless at 450 approximately how long does it take to cook? But cooking the lamb at 450 is going to make a mess of your oven. How long should the lamb sit at room temperature before cooking?
 
amysarah
amysarah December 24, 2011
It also depends on whether you're doing the boned leg 'as is' (i.e., a big flat-ish piece) or rolling it, in which case you'll have a thicker, denser roast which will take a bit longer than unrolled.

Btw, rolling a boned leg around fresh herbs (e.g., rosemary, thyme, parsley), garlic, s&p and tying it works well and is easier to cook to a uniform temp...I usually do it rolled as a roast, but flat on the grill - having some parts rarer than others is sometimes useful when feeding a group with varying tastes.
 
bella S.
bella S. December 24, 2011
Yes, amysarah, the roast will be rolled for even cooking.
 
nutcakes
nutcakes December 24, 2011
I like your plan, the 450 will promote browning, but I'd cook it at 300-325 instead of 350. It will take much less time than a bone-in roast. Start checking the internal temperature after 30 minutes at the lower temperature, then at least every 10 minutes until it reaches 135F. Tent with foil and let rest 10-15 min before carving.
 
bella S.
bella S. December 24, 2011
Thanks, Nutcakes. I had thought that boneless would cook faster, but Amanda said that bone-in cooks faster. I like your idea of turning the oven down a bit. I guess that I just need to keep an eye on it.
 
Amanda H.
Amanda H. December 24, 2011
Yes, I'd keep the initial 450, and then it might take longer -- bone in cooks faster. But keep checking it!
 
bella S.
bella S. December 24, 2011
Thanks Amanda. I didn't realize that bone-in cooks faster. Does the bone conduct the heat?
 
nutcakes
nutcakes December 24, 2011
Do you really think it is shorter time for bone in on a smaller roast like this?
 
bella S.
bella S. December 24, 2011
nutcakes, I didn't know that bone-in cooks faster until I read Amanda's answer. For some reason I thought just the opposite. The 4.27lb. roast that I have is boneless. I will be cooking it rolled up, not flattened out. I really wanted to have a plan ahead of time, because I don't want to be opening the oven a lot to check on the roast. That being said, I will open the oven door as much as I need to, to make sure that the meat does not go beyond medium rare.
 
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