Remove fat from fillets, if any. Cut the meat into strips approximately 1.5 cm wide. Place the fillets in a plastic bag with fasteners.
In a separate bowl, prepare the beef kebab marinade. Combine soy sauce, vinegar, brown sugar, onions, vegetable oil, minced garlic, ginger and black pepper.
Pour the marinade into a bag of meat and mix well. Fasten the bag and put in the refrigerator for 2-3 hours.
Turn on the grill to preheat to medium heat.
Remove the meat from the marinade and string on metal skewers.
Place the kebabs on the grill rack and cook the beef kebab, turning occasionally, for 7-10 minutes, until medium cooked.