I have to say, I think that grilling peppers is the most idiot proof of all grilled vegetables.
Approximate quantities: 3 large bell peppers, halved; 2 tablespoons of olive oil; 2 tablespoons of grapeseed oil; 6 garlic cloves, peeled and crushed; salt and pepper
Cut the peppers along their seams, all the way around, and remove the seeds and stems, place skin-side down in a large, rectangular Pyrex baking dish drizzle with oils and generously sprinkle generously with salt and pepper and then place a crushed garlic clove in each pepper an hour or so before grilling
Place on the grill skin-side down and grill at a medium-high to high heat for 8-10 minutes, turning them half way through per side; allow to cool and then chop roughly
If you prefer them without the skin, just leave them on for 8-10 minutes and then, when they are cool enough to handle, the charred skins will easily peel off
The variable here is your grill and it’s temperatures. I’ve provided a heat and time range for everything that should work for almost all grills.
Almost everything needs to be turned, or if it’s in a grill basket a good shake at the halfway point will work, so what I’d recommend is plan to check it and turn it halfway through the shorter time range that I suggest, and then, to check it again for doneness, at the end of the shorter time range. This way, if you grill doesn’t run as hot, and you can see that you need more time, it’s easy to leave the second side on for a few more minutes.