In a large bowl, whisk together the orange juice, orange zest, peanut butter, sugar, soy, ginger, garlic, and red pepper flakes until smooth and evenly combined. Reserve 1/3 cup of the mixture to serve as a dipping sauce. Put the marinade in a resalable plastic bag, add the chicken, seal the bag and turn to coat evenly. Refrigerate and allow to marinate for 30 minutes or up to 2 hours.
Heat a grill to medium heat, (350 degrees F), and rub the grate with a towel dipped in oil. Thread 1 to 2 chicken tenders on each skewer. Grill the chicken until thoroughly cooked, about 2 to 3 minutes per side. Transfer to a serving platter and sprinkle with cilantro and peanuts. Serve hot or at room temperature with the reserved peanut sauce.