Prepare the Marinade: In a large mixing bowl, whisk together the extra virgin olive oil, white vinegar, soy sauce, Worcestershire sauce, and lemon juice until fully combined. Add the brown sugar, pepper, salt, and garlic powder to the liquid mixture. Whisk until the brown sugar is completely dissolved and the spices are evenly distributed throughout the marinade.
Marinate the Chicken: Place the chicken cutlets in a large resealable plastic bag or a shallow dish that's large enough to hold them in a single layer. Pour half of the marinade over the chicken, making sure each piece is well-coated. If using a bag, seal it tightly, then gently shake it to ensure the marinade covers all the chicken pieces. In a dish, simply turn the chicken breasts over a few times to coat them well.
Refrigerate: Refrigerate and marinate for at least 30 minutes, or for best results, overnight. The longer the chicken marinades, the more flavorful it will be.
Make a Glaze: Pour the extra half of the marinade into a small saucepan and bring to a simmer over medium heat until it reduces a bit. Stir as it thickens for about 3 minutes then remove from heat and let cool to room temperature. This makes a delicious glaze to pour over the cooked chicken later.
Grill the Chicken: Preheat your grill to medium-high heat. Remove the chicken from the marinade, letting any excess drip off. Discard the remaining marinade. Place the chicken on the grill and cook for 6-7 minutes per side, or until the internal temperature reaches 165°F and the juices run clear. The actual cooking time may vary depending on the thickness of your chicken breasts.
Serve: Once cooked, let the chicken rest for a few minutes to allow the juices to redistribute throughout the meat.