Cut the cucumber and tomatoes into 1—2 cm (½—¾ inch) chunks and put them in a large salad bowl. Cut the flesh from the peppers and carefully remove the ribs and the seeds. Cut the pepper flesh into thin strips and put them in the bowl with the cucumbers and tomatoes. Finely slice the red onion and add to the bowl with the olives.
Make the dressing by whisking the oil and parsley. Season to taste with salt and pepper.
Pour the dressing over the salad and toss carefully. Transfer to serving bowls, scatter some feta evenly over each bowl and serve.