To make the marinade: whisk together all the ingredients in a medium bowl and set aside.
To make the chicken: wash chicken with cold water and pat dry with a paper towel.
Carefully cut a pocket into the side of the chicken breast using a thin bladed knife (I use a boning knife). Place pocketed chicken breasts into a large zip lock plastic bag and pour three fourths of the marinade over the chicken.
Press most of the air out of the bag and seal tightly.
In a separate small zip lock bag, place julienned peppers and onion and pour in the remaining marinade. Press out the air and seal tightly.
Refrigerate for 30 minutes to 2 hours, turning occasionally.
Preheat grill to medium high heat. Remove chicken and vegetables and reserve the marinade.
Pour marinade into a medium sauce pan, and bring to a boil for one minute. Remove from heat and let cool.
Stuff vegetables into chicken breast pockets and close pockets with toothpicks.
Lightly spray with vegetable oil. Grill over direct medium heat 5 minutes on each side turning and basting with the remaining marinade once half way through grilling time.
Serve warm over quinoa or brown rice with cucumber yuzu salad. Don’t forget to remove the toothpicks!
Combine all ingredients in a medium bowl, lightly toss and serve.