Make the marinade - In a bowl, whisk together the ketchup, soy sauce, brown sugar, rice vinegar, ginger, garlic, salt, and pepper. Reserve a ½ cup for basting, and refrigerate until ready to use.
Marinate the Chicken - Add the chicken to a baking dish or resealable plastic bag. Pour in the marinade and turn the pieces to coat evenly. Tightly cover or reseal and transfer to the refrigerator for at least 3 hours or up to 24 hours.
Preheat the Grill - Preheat the grill over medium-high heat between 375 to 400ºF (191 to 204ºC). Clean and carefully grease the cooking grates with the oil.
Grill the Chicken - Place the meat on the grill and close the lid. Cook for 5 minutes then flip and baste with the reserved sauce. Cook covered for about 5 minutes then flip and baste. Cook for about 2 to 3 minutes then flip, baste, cover, and cook for 2 to 3 minutes.Cook until the internal temperature reaches about 165 to 170ºF (74 to 77ºC). If browning quickly, move the chicken to the indirect heat side of the grill to finish.
To Serve - Cover the chicken with foil to keep warm. Rest for 5 minutes before slicing or serving. Garnish with green onions.
Servings: About 12 smaller pieces, varies by brand
Marinade: Makes 1 ½ cups
Storing: Store chicken in an airtight container in the refrigerator for up to 5 days. Store marinade for up to 2 days in the refrigerator.
Reheating: Cover and microwave the chicken on high heat in 15 to 30-second increments until hot.
Ketchup Substitute: Combine ¼ cup tomato paste and ½ cup water or pineapple juice. Add ½ cup of the mixture to the sauce. If desired, add ½ teaspoon onion powder.
Make it Gluten-Free: Substitute soy sauce with gluten-free tamari or coconut aminos.