Preheat the oven to 425 degrees. Line a baking sheet with tin foil and coat with cooking spray.
Cut the fingerling potatoes in half and place on the baking sheet. Drizzle 1-2 tsp olive oil on the potatoes and season with sea salt and freshly cracked pepper, to taste. Toss to coat evenly then place in the oven and roast for 15-20 minutes, or until tender.
While the potatoes roast, make the dressing: In a small bowl, combine the olive oil, lemon juice, red wine vinegar, Dijon mustard, minced garlic, oregano, sea salt and freshly cracked pepper, to taste. Whisk until well blended then set aside.
Remove the potatoes from the oven, toss with half of the vinaigrette and set aside until they cool.
Once the potatoes are cooled, add the grape tomatoes, red onion, kalamata olives, parsley, and feta cheese.
Drizzle the remaining vinaigrette on top and toss to coat evenly. Serve immediately. Enjoy.