a 3# steak is more like a small roast. so lets cook it like a small bone in rib roast. You could do it solely on the grill if you have 2 zones, but I prefer to do some smoke and reverse sear. Chilie is right go by IT for sure but lets break down quickly the rev sear.
a few hours before the cook put either
1. salt/pepper/garlic (AP rub for the Malcolm Reed crowd) or
2. a hardy beef rub with minimal sugar or sweetness.
I highly recommend 1 because God made that cow taste great the way it is and your really dont need to season much to make the flavors of the natural beef taste amazing!
then heat your smoker to 225-250 degrees, put your steak/roast on for about an hour to hour and half or about to 120 IT. (whichever is first)
then make sure whatever grill you use is really hot (like 400 degrees at least) or you can use a broiler in the oven in a pinch
throw on the grill and sear the edges until the meat is about 130 IT (should be about 90-120 seconds each side) or alternatively let your meat rest 30 minutes slice in two to four steaks (depending on how thin you want it) and then sear the individual pieces to the tastes of those eating it.
If you do the first method and just sear it whole then you can slice it laterally and cut roast like pieces for the whole family.
Make sure after you sear to let your meat rest 30-45 minutes before slicing (i like to wrap mine in foil for some carry over and get the IT up a few more degrees).. you will find it it juicier that way...
Let me find some pics to demonstrate the above methods....
season
smoke
here is a pic of searing a cowboy on the grill
all done
full disclosure this was a combo of two different smokes but it was better to have the right pics to demo the process.
Hope this helps!
Happy Smoking(beef!),
phatbac (Aaron)