Remove lower stems of the parsley, rinse and pat dry (I use a salad spinner for this).
In the bowl of a food processor, add parsley, garlic, vinegar, fresh thyme, onion, fresh basil, ½ teaspoon salt, ¼ teaspoon pepper and red pepper flakes.
Process until smooth, pour into a medium-size bowl and set aside.
Heat the grill to medium heat.
While grill is heating up, slice the peaches in half, remove the pit and baste each side with 1 teaspoon olive oil
Grill peaches 4 minutes each side. Set aside to cool.
Chop tomatoes, making sure to remove the seeds.
Next chop the cooled peaches.
Stir the remaining 6 tablespoon of olive oil into the chopped herb mixture until combined. Add peaches and tomatoes. Cover with plastic wrap and let the mixture sit for 2-3 hours to marinate.
Preheat the grill to medium. Season with steaks with salt and pepper.
Grill 11-14 minutes for a 1" thick strip on charcoal or 11-15 minutes on a gas grill to desired doneness (145 degrees F for med-rare and 160 degrees F for medium.
Remove from the grill and allow the steaks to rest for 5 minutes. Spoon sauce over steak and serve.