1. Place the halved potatoes in a large pot and cover with cold, salted water. Bring to a boil over medium-high heat.
2. Cook the potatoes until just tender when pierced with a fork, about 15-20 minutes depending on their size. Be careful not to overcook—they should hold their shape well.
3. Drain the potatoes and let them cool slightly before transferring to a large mixing bowl.
4. While the potatoes cool, whisk together the olive oil, lemon juice, minced garlic, oregano, and red wine vinegar (if using) in a small bowl. Season with salt and pepper to taste.
5. Add the sliced red onion to the dressing to soften its bite, letting it marinate for about 5 minutes.
6. Pour the dressing and onions over the warm potatoes and gently toss to coat all the pieces evenly. The warmth helps the potatoes absorb the flavors beautifully.
7. Fold in the Kalamata olives, diced cucumber, and chopped parsley, mixing carefully so the salad remains chunky and fresh.
8. Sprinkle the crumbled feta on top just before serving for a creamy, salty finish.

One little trick Mama Lou taught me was to use warm potatoes in this salad because they soak up the dressing more deeply—something I always keep in mind when making this at home. Also, I like to give everything a gentle toss so the potatoes don’t break apart, preserving that rustic, homemade feel.