If you barbecue a thick or tough cut of meat, you may well need to cook it first, before marinating it and subjecting it to the fiercely hot coals. But what if you are cooking it indoors? Do you still need a two-stage process, when you can get decent results by simply putting the marinated meat in a low to medium oven?
I often buy spare rib chops, cut them into pieces, coat them in a marinade, and cook them in a low oven. But this cut gives off quite a bit of liquid, which you have to allow to evaporate before the meat browns and the marinade turns sticky. You don't know how long that will take, and you may have to fiddle with the oven temperature to speed the process. The pork can become tough.
I poached four chops (in a pot with a chicken carcass - they contributed to the resultant stock) for about 50 minutes. Then I cut them up and marinated them. Later I cooked them under the grill until browned and warmed through, first on a high heat, then on a lower one.
It works better than the one-stage method, I think. The meat is more tender, and the marinade penetrates it more efficiently.
Marinade recipes here and here.