In a medium bowl whisk together balsamic vinegar, honey, garlic, Italian seasoning, salt, black pepper, and crushed red pepper (if using).
Place chicken breasts in the marinade and marinate for 3 hours or overnight.
Preheat over to 375 degrees.
Place chicken and broccoli on opposite ends of a sheet pan.
Bake for 30-40 minutes or until chicken is cooked through and no longer pink in the center. The internal temperature should be 165 degrees.
Serve with rice, quinoa, or as is.