best way to grill leeks?

As part of a big dinner I am planning on making grilled leeks with romesco sauce. I have looked at a number of different recipes and they seem to vary widely on the best way to grill the leeks. A number of recipes have you cut and then parboil the leeks prior to grilling, and some go straight onto the grill directly after cutting in half and brushing with oil. I would rather skip the extra step but am unsure that the leeks will become tender enough without it. Just wondering if anyone has any personal experience to share on how they have done this in the past? Thank you for any tips.

I've tried it without the parboil method without great results. But like you, I hate extra steps, so here's what I do now: wrap the leaks in foil with a bit of water, then onto the grill for about 20 minutes. Remove from foil packet and grill direct over coals for another few minutes.

Another option is to grill them directly, then throw them into a paper bag to steam for a while.