Preheat the grill. Heat the oil in a large pan. Add onions and courgettes and cook until onions have softened.
Season with salt and freshly ground black pepper and sprinkle thyme over.
Stir in the quartered potatoes and remove from the heat.
Beat the eggs together and pour over the vegetables in the pan.
Cook on a very low heat until the egg has just about set.
Remove from the heat and place under the grill. Cook until egg has completely set.
Remove and cut into big wedges. Either stuff into toasted pitas or serve with pitas on the side.
COOK'S NOTE: You can use any leftovers, from meat to peppers, in a frittata. It is delicious cold, which makes it a perfect lunchbox or picnic treat.