Mix together all of the marinade ingredients. For added ease, you may do this right in a resealable bag. (Place it in a bowl or a baking sheet with sides so it doesn’t spill out.)
Prior to grilling, allow the chicken to marinate in the refrigerator for at least several hours and up to all day. Seafood and vegetables are best soaked for at least 20-30 minutes but not more than two hours. When grilling vegetables, too, marinate in a separate bag. Flipping the bag from time to time will redistribute the liquid throughout the items being marinated.
When ready to eat, allow the chicken to sit at room temperature as the grill is preheating. Drain and discard the marinade, and then grill the chicken over medium-high heat for 7-8 minutes per side or until the internal temperature reaches 165 degrees F. Total cooking time will vary based on size of chicken breast. Remove to a platter and allow the chicken to rest for 5 to 10 minutes before serving.
When grilling vegetables, cook for just long enough for grill marks to appear and the veggies to become crisp-tender. I like to slice zucchini lengthwise in thick slices instead of rounds, which are more likely to fall through the grates. Thicker slices will develop a nice sear without turning mushy. Thicker slices of onion or a hard vegetable like carrots will require a few extra minutes on the grill. Scallions are delicious and cook quite quickly.