Preheat a gas or charcoal grill on high heat. Oil the grates.
Rub the peaches and corn with 2 teaspoons olive oil.
Grill the peaches until they have grill marks, about 1-2 minutes per side. Also, grill the corn, turning occasionally until lightly charred, about 5-7 minutes.
Let the corn cool slightly before slicing off the kernels.
In a large bowl, combine the corn, arugula, quinoa, tomatoes, pecorino and chives.
For the vinaigrette, whisk together the vinegar, 3 tablespoons olive oil, mustard, salt and pepper in a small bowl.
Drizzle the dressing into the salad, tossing to combine.
Arrange the salad on a serving plate or in a bowl and top with grilled peaches.