Make the marinade - In a bowl, whisk together the ketchup, soy sauce, brown sugar, rice vinegar, ginger, garlic, salt, and pepper. Reserve 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 and baste, then cover and cook for 2 to 3 minutes.Cook until the internal temperature reaches about 165 to 170ºF (74 to 77ºC) on a meat thermometer. If the chicken is browning too quickly, move it 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.
Notes
Servings: About 12 smaller pieces, varies by brand
Marinade: Makes 1 ½ cups
Storing: Store 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.