For a couple of large portions:
Preheat the oven to 200°C ready to roast the peppers. Put the quinoa in a saucepan and cover with twice its depth of cold water. Bring to the boil and simmer until cooked, about 15 minutes (or follow packet instructions if different). When done it will be soft but the seed will still be slightly firm. Drain any remaining water and set aside to cool.
Meanwhile, roast the peppers. Place whole on a baking sheet in the preheated oven. Cook until the skin is blistering and blackening, turning once or twice - this will take about 10 minutes. As soon as they are out of the oven (they should be on the point of collapsing), put in a bowl and seal with clingfilm, or pop them in a sandwich bag and seal. Let them steam until cool, at which point take them out and remove the stem and internal waste and peel, retaining as much of the juice that runs off as possible. The skin should pull off easily. Slice thinly lengthways and set aside until the quinoa is cool.
Finely chop the onion. Drain and rinse the sweetcorn thoroughly, and drain again. Dry fry the pinenuts until golden, shaking regularly to stop any sticking and burning. Assemble the salad by mixing the chopped peppers, sweetcorn, chopped onion and toasted pinenuts. Whisk the vinegar and oil together, chucking in and pepper juices too, then stir into the salad. Crumble over the feta, and enjoy, possibly with a tomato alongside.