First make the marinade. Add balsamic vinegar, coconut aminos, olive oil, granulated garlic, granulated onion, and salt and pepper to a small mixing bowl. Whisk all of the ingredients together.
Add chicken thighs to a medium bowl and pour marinade over chicken. Ensure chicken is evenly coated in marinade. Refrigerate for at least 2 hours, but overnight is even better.
Remove chicken from the refrigerator when ready to start grilling peaches.
Heat a grill pan over medium-high heat. Bush both sides of peaches with olive oil and place cut-side down hot grill pan, about 4 minutes. Flip peaches and grill on skin-side until very soft, about another 4 minutes. Remove peaches from grill, add to a platter and set aside.
Carefully wipe down grill pan to remove any remnants from the peaches so it doesn't start to burn.
Next, add chicken thighs to hot grill and grill for about 8 minutes. Flip and cook for about 6 minutes, or until internal temperature reaches 165 degrees F. Remove chicken and add to platter with peaches.
Garnish with sliced green onions and serve.
