Combine the first 4 ingredients in a bowl. Cover and marinate in the refrigerator 30 minutes.
Heat 2 Tbsp. of the oil in a wok or wide skillet set over high heat. Add the chicken, stir-fry until just cooked through, about 3 to 4 minutes, and then transfer to a plate.
Clean the wok or skillet. On a medium-high heat add remaining oil to skillet. When hot, add the ginger, garlic and bell pepper and stir-fry 30 seconds. Return the chicken to the pan along with peanuts and sauce mixture. Cook until the sauce thickens and coats the chicken. Sprinkle with green onion and serve.