Place chicken in a large gallon-size ziplock bag. Sprinkle with steak seasoning and press it into the surface of the chicken with your hands.

Add balsamic vinegar, olive oil, 1/4 cup brown sugar, and lemon juice to the bag. Seal and shake to coat evenly. Place bag inside a deep plate to catch any leaks.

Marinate in the refrigerator for at least 4 hours, or up to 48 hours. A minimum of 30 minutes works if short on time.

Set a small saucepan under a colander and strain the chicken through it to collect the marinade. Set chicken aside on a plate.

Preheat your grill to high heat and oil the grates. Place chicken over direct heat, close the lid, and sear for 2 to 3 minutes until browned with grill marks.

Flip the chicken with tongs and move to the indirect heat side of the grill. Turn off that burner and reduce the other to medium-low, between 250 and 275 degrees F. Cover and cook for 30 to 50 minutes depending on thickness, brushing with reserved marinade once or twice.

The chicken is done when it reaches an internal temperature of 165 degrees F on a meat thermometer and juices run clear.

Pour the reserved marinade into the saucepan over medium-high heat. Add 2 tablespoons brown sugar. Bring to a boil, then reduce to a simmer for 5 to 10 minutes until thickened. Drizzle over grilled chicken before serving.