When I was a kid, I read a story about a 24-hour Thanksgiving turkey. Apparently, such a dish was commonplace for large families – a turkey so big it actually took 24 hours to cook. And now I’m thinking that it’s a little implausible, no oven, however low in heat, should take that long to cook any size chuck of meat. A quick Goggle points me to a turkey that gets an 18 hour marinade with a two hour roasting, how that even adds up to 24 doesn’t even figure for me. So, in their early days, did any Doper know of a turkey that took a ridiculous amount of time to cook, either because of it’s size or the oven’s heating ability/cooking method?
I haven’t heard of a turkey that actually NEEDED that long to cook, but I’ve heard lots of stories of clueless cooks who think that 200 degrees overnight or something is the way to cook a turkey. And I’ve had plenty of turkey that’s tasted like it’s been cooked for 24 hours.
Well, if you count brining it, then easily, as I like to brine a turkey for 24 hours before I smoke it. The largest bird I did this with was a 22 pounder, took a little more than 12 hours to smoke, wasn’t bad, but certainly wasn’t the best bird I’ve cooked.
I can’t imagine trying to smoke anything larger than that, and even that was pushing it. I really can’t imagine a slower way to cook a turkey than smoking, and I’m rather scared to try.
Yeah, I too, cannot imagine a turkey so big that would take that long to cook. Even at 200, I’d expect it to be done within 18 hours, probably more like 12. An average turkey, about, say, 12-15 pounds, takes me 4-6 hours to cook at 225-250 on a smoker. I could see something like brisket or a whole pork shoulder taking up to 24 hours if it’s a 12+ pound hunk and cooked at around, say, 200-210, but there’s other variables going on there. (Mainly, this type of meat tends to plateau at around 160-175 for several hours as the collagen renders into gelatin and it benefits from long, slow cooking up to this temp.) A turkey, though, especially the breast, does not get better from this same technique. Add to that the awful flabby skin you get from such a cooking method, and that’s just not a good way to cook a turkey.
A friend’s wife made a turkey one holiday, and ISTR that she cooked it a long, long time. I don’t know whether it was her intention (i.e., planned ahead of time, or an attempt at a save), but the rather dry meat was mixed into the stuffing with cranberries.
Her father, who came over, was not pleased.
Well, if you let them get to 2 years old they can weigh 40+ pounds … and take forever to cook unstuffed. Not 24 hours, but a good solid 12 hours.
Does that 24 hours have to be cooking? a 12-16 hour brine session can eat up more than half of that time 
My aunt did this last Thanksgiving, or close to it, anyway. And I think she’s still pissed off at me for suggesting that maybe it wasn’t such a good idea.
Needless to say, I’m never eating her turkey again.
I first saw the low heat (overnight) turkey recipe from a cookbook by Adele Davis in the 60’s. I have had many successful 185 degree turkeys since then. For a recent description see: How to Cook the Perfect Turkey - Nutrition. Good luck and enjoy. 
When will people learn that cooking turkey at 450 F is the way Jesus intended? High roast. Say it with me. High roast. These lukewarm turkey-sauna people are insane.
24-hour cooking is necessary if the turkey is one of those big grey ones that eat peanuts and have long noses.
What if the turkey starts out frozen, and defrosts as it cooks (not that anyone should eat it)?
I’ve done the low, slow overnight roast many time and it’s amazing!! Always moist and flavorful. Then I got a rotisserie, and I’ll never do a turkey in the oven again…
Surely thou dost jest.