Place the quartered potatoes in a large pot and cover with cold salted water. Bring to a boil over high heat.

Reduce heat and simmer the potatoes for 15-20 minutes, or until they are easily pierced with a fork but not falling apart. Drain immediately and let them cool slightly for 5 minutes.

While potatoes cook, prepare the vinaigrette: In a small bowl or jar, whisk together the lemon juice, olive oil, Dijon mustard, minced garlic, oregano, salt, and pepper until emulsified.

While the potatoes are still warm (this helps them absorb the dressing), place them in a large mixing bowl. Pour about half of the vinaigrette over the potatoes and gently toss to coat. The warmth of the potatoes will help soak up the flavors.

Add the diced red onion, fresh parsley, and dill to the bowl. Pour in the remaining vinaigrette and gently fold everything together until evenly mixed. Be careful not to mash the potatoes.

Taste and adjust seasoning if necessary (more salt, pepper, or a squeeze of lemon). Allow the salad to rest at room temperature for at least 15 minutes, or chill in the refrigerator for 1 hour before serving for the best flavor development.