This recipe I got from the good people in the Ontanagon, Michigan in the U.P. They use this for venison roasts, but it work good with regular beef roasts too. Put roast in a Dutch oven and add one can of Coke, one envelope of dried onion soup mix and a can of golden mushroom soup. It must be golden Mushroom soup. Cover and cook at 300 degrees until done. A 4 lb. roast usually takes between 3 1/2 to 4 hrs. Then if theres left overs I add beef boullion to the gravy and make hot roast beef sandwiches.
Marinade for smoker bath for fixing pork barbeque:

1 can of Dr. Pepper
2 cups cider vinegar
1 cup water
3 tbs grd. black pepper
2 tbs salt
1 tbs worcestershire sauce
1 tbs. paprika
1 tbs. chilli powder