To marinate: place chicken in a nonporous glass dish or bowl. Pour 1 1/2 cups of wine over chicken then sprinkle with garlic powder and onion powder. Cover and refrigerate to marinate for at least 1 hour.
Heat vegetable oil in a small frypan over medium heat. Saute onion and capsicum for 5 to 7 minutes or until soft. Remove from frypan and set aside.
Remove chicken from marinade, discarding any remaining marinade. Heat olive oil in a medium frypan over medium high heat and brown chicken, adding teriyaki sauce to 'sear'. Braise with remaining white wine and simmer for 8 to 10 minutes or until chicken is cooked through and no longer pink inside.
Add onion/capsicum mixture to chicken and heat through, stirring. Serve hot.