Rinse and scrub the potatoes, then cut them into halves or bite-size pieces. Add them to a pot or saucepan of salted water and bring to a boil. Cook until fork tender but not falling apart.
Drain the potatoes and let them cool completely.
Add the cooled potatoes to a large bowl. Add the halved olives and sliced tomatoes.
In a small bowl, combine olive oil, vinegar, and a small splash of olive brine. Add the sliced red onion along with fresh chopped oregano, fresh dill, and dried oregano. Let it sit briefly to soften and build flavor.
Pour the vinaigrette over the potatoes, olives, and tomatoes. Toss gently to coat.
Crumble in the feta and add salt and black pepper to taste.
Toss gently again, keeping everything intact. Let sit for a few minutes before serving.
