In a large resealable plastic bag, combine the soy sauce, brown sugar, cider vinegar, Worcestershire sauce, Dijon mustard, ground pepper, and olive oil. Seal the bag and shake well to combine all the marinade ingredients.

Add the beef cubes to the bag and reseal it. Gently massage the bag to ensure all the meat is coated. Place in the refrigerator to marinate for at least one hour, or up to eight hours for maximum flavor.

When you are ready to cook, preheat your grill to medium high heat.

If using wooden skewers, ensure they have been soaked in water. Thread the beef and bell peppers onto the skewers in an alternating pattern.

Place the skewers on the hot grill. Cook for about four to five minutes per side. You are looking for a nice char on the outside and a medium pink center.

Remove from the grill and let the meat rest for a few minutes. Sprinkle with fresh parsley and serve immediately.