Has anyone cooked a chuck roast and a pork butt at the same time?
Will they finish at close to the same time?
Most of my family prefer pork but I would rather have beef.
Any advice or tips are greatly appreciated.

A timely question! I actually tried it last night. The chuck didn't take as long, but they cooked well at the same temp. I had it at 170 for the first hour and a half. Bumped it up to 200 for three hours and then 250 until done. I don't remember the ending times, but the pork took a couple hours longer.

About 3 hours in
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Would cooking in cast iron vs an aluminum pan speed up cooking times?

Would cooking in cast iron vs an aluminum pan speed up cooking times?

Good question, I never thought to take that into consideration. I will test it sometime with two identical pieces of meat.

Let me know when those next two hunks of meat go on the smoke, JD.
You may need some judging of the end results, and I ain't that far away.

Put them both on the smoker at 250°-275° at the same time.  If you wrap them both at about 160° IT, they will finish in the 8-10 hour range.

I've started cooking both of them the same way.  Put rub on them and onto the smoker.  At 160° or so, place them in a pan with beer and cover with foil.  Continue with cook until they hit 200°-205° IT, pull in the pan with the liquid, sprinkle on more rub, drain off any excess liquid, eat.  I don't worry about letting juices settle because it is already in a liquid when you are going to pull it and it isn't going to dry out.

Has anyone cooked a chuck roast and a pork butt at the same time?  Yes
Will they finish at close to the same time?  Yes

Just like cooking two butts at the same time, one will finish faster than the other, maybe you're hot right to left or left to right.  Maybe one is a pound or so heavier. 

Either way, I think the simple answer to your inquiry is yes, these two meats are highly complimentary and cooking at the same time with same process is very doable.    Last time I did this was for a modest catering gig, three butts and three chuck roasts.  Now I did have 8 lb chuck roasts so they were the same size as the butts.   All finished at roughly the same time. 

DK