Cut the red pepper, courgette and red onion into strips.
Heat a little oil in a griddle pan (or a frying pan, if you don't have a griddle pan). Add the vegetables, and cook over a fairly high heat for 5 minutes, tossing regularly, until the vegetables are soft and lightly charred.
In a small bowl, combine the balsamic vinegar with the dried oregano and some salt and pepper. Pour the mixture over the cooked vegetables, and return to the heat for another minute or two.
To make the yogurt dressing, add the garlic and parsley to a mini food processor, and blitz until finely chopped. Add the yogurt, lemon juice, and plenty of salt and pepper, and blitz again to combine.
To assemble, divide the vegetables between the four tortillas / flatbread, and top with the herby yogurt dressing and some crumbled feta cheese.