Place potatoes in a large pot and cover with cold, salted water. Bring to a boil and cook until just tender, about 12–15 minutes. Drain well and let them rest for a few minutes so excess moisture evaporates.
In a small bowl, whisk together the olive oil and vinegar. Season with salt and pepper.
While the potatoes are still warm, place them in a large bowl. Add the sliced red onion and pour the dressing over top. Gently toss to coat, being careful not to mash the potatoes.
Sprinkle with parsley and herbs, toss lightly again, and adjust seasoning if needed. Serve warm or at room temperature.
