In a medium bowl, whisk together balsamic vinegar, lemon juice, olive oil, Dijon, brown sugar, Worcestershire, garlic, thyme, oregano and rosemary; season with salt and pepper, to taste. Reserve 1/4 cup and set aside.
In a gallon size Ziploc bag or large bowl, combine chicken and balsamic vinegar mixture; marinate for at least 1 hour to overnight, turning the bag occasionally. Drain the chicken from the marinade.
Preheat grill to medium high heat.
Add chicken to grill and cook, flipping once and basting with reserved 1/4 cup marinade until cooked through, reaching an internal temperature of 165 degrees F, about 5-6 minutes per side.
Serve immediately, garnished with parsley, if desired.
Notes
An outdoor grill is not necessary. Too cold to grill outside? A cast iron grill pan can be used to get those favorited grill marks and charred flavor. These can also be baked at 400°F for 15-20 minutes, brushing with the reserved marinade during the last few minutes of cook time.
Preheat the grill. Ensure that the grill is properly cleaned (to prevent sticking) and preheated prior to grilling. This will allow for a better sear for those grill marks and evenly cooked chicken.
Marinate for at least 1 hour. For the best flavor and texture, marinate the chicken for at least 1 hour (to overnight). This will help tenderize the meat and lock in moisture when cooked.
Use an instant-read thermometer for the most accurate results. The internal temperature should reach 165°F.
Use similar size chicken. Chicken breasts come in a variety of sizes - try to use similar-sized chicken breasts, pounding out the chicken as needed into flat, even pieces for even cooking and grilling.
Let your meat rest. Let your chicken rest for at least 5 minutes prior to serving, allowing the juices to redistribute – this will allow for maximum flavor and juiciness.
Reheat in the oven. Leftover chicken can be rubbery when reheated. For best results with leftovers, reheat in the oven at 350°F, covered in aluminum foil until warmed through.