[bluesman]

It's time and temperature. At a cooking temperature between 300 and 350 degrees F, it takes a chicken around 20 to 30 minutes per pound to cook. A 4 pound chicken should take around 2 hours to cook. When the internal temperature of the chicken reaches 175 to 180 degree F, it's time to take it off the heat.

So it will depend on your BBQ temp. Obviously, the lower the temp, the longer it will take to cook the bird. I use a spit on my Weber kettle and it takes about 2 hrs @ 300F for a 4-5 lb bird to reach 175F near the thigh.

[1vertical]

Here is a KICK ASS poultry smoke thang i love.

suspend the bird above a  mix of Black tea leaves, Orange peel pieces, and brown sugar,
in a tin pie pan ....put hot fire under the tin pan and smoke the beejeans out of the bird
for a bit...then cook bird in oven or grill  to your finished doneness mode.

[punatic]

Now there is a thoughtful post.   

[Slowbrew]

On a bit happier note...

We smoked 2 chickens this weekend at 280F for 3 - 4 hours.  Used Mesquite and Hickory with a spice rub (sea salt, yellow mustard powder, garlic powder, onion powder, a bit of cumin and cayenne). Very moist and tender.

(and almost no "soaked in a sewer" flavor at all  )

Paul