The trick to smoking a tenderloin and not drying it out is indirect heat. Until I got my Kamado Joe I smoked them on a Brinkman barrel smoker, not the upright, but the kind with the firebox on the side. Cooking time varies on how big the tenderloin is. I like mine medium rare. I would smoke at about 275 deg for about an hr. I would cut into it and check the center a few times till it was where I liked it. Remember it will continue to cook a little once you take it off so account for that.

I almost never marinated it, just threw it on raw and let the smoke flavor it. I since have done several where I marinated it overnight in Moores teriyaki. If you only leave it in the marinade for about 8-9 hours it leaves it with just a hint of sweetness to go with the smoke flavor, no overpowering teriyaki flavor. It you want to make it really good, after you marinade it cut some 1/4 inch slits down the tendeloin and slide in cut pieces of garlic cloves about every couple inches. Smoke to desired doneness and you are lip smacking ready. It will be real moist and I'll put it up against anything beef tenderloin you might buy in a restaurant. I need to kill about 10 or 15 this year because I get requests at every get together to bring tenderloin and there is never anything left. I have one ternderloin left and it is being cooked next weekend for the AL/LSU game.