Cut chicken breasts in half crosswise.
Using a meat tenderizing mallet, heavy skillet, or rolling pin, pound the chicken between two pieces of plastic wrap until it is a uniform thickness.
Place Chicken and marinade in a large zip top bag or large container for marinating.
Place in the refrigerator and marinate for 2 to 4 hours.
Remove the chicken 20-30 minutes before cooking and allow it to come up to room temperature.
Preheat grill to medium high heat.
Place chicken on the grill and cook for 5-7 minutes on the first side. The chicken will release easily from the grill when it is time to flip it.
Flip chicken and grill for an additional 5-7 minutes.
Using a thermometer like this one is great for letting you know the chicken is at the proper temperature. Boneless Chicken Breasts are perfect at 165℉ and Boneless Chicken Thighs are ready at 170℉.
Remove the garlic and herb chicken from grill and serve with your favorite side dishes.