Peel and halve the onion and slice or cut into thin strips. Wash the tomatoes and cut into pieces. Wash cucumbers, peel if necessary, cut them in half lengthwise and cut them into slices. Drain the olives.
Peel and finely chop the garlic.
Mix yoghurt, garlic, vinegar and oil. Season to taste with salt and pepper. Crumble the feta coarsely. Mix prepared salad ingredients, feta and yoghurt cream. Season to taste with salt and pepper.