1) Preheat a grill pan to medium-high heat.
2) For the dressing, combine the rice wine vinegar and Dijon in a small bowl. Slowly pour the olive into the bowl, whisking constantly to emulsify. Season with salt.
3) For the salad, place the peaches in a bowl and drizzle with olive oil. Sprinkle with salt and toss well. Place on the grill and cook for 1 to 2 minutes on each side.
4) Place the mesclun mix in a large bowl. Add chopped pecans, feta, and cooked peaches. Drizzle salad with dressing and toss to coat.