Slice the beef for bulgogi thinly.
Julienne the onion, green onion, and carrot.
In a bowl, mix soy sauce, sugar, minced garlic, sesame oil, and pepper to make the marinade.
Marinate the beef and vegetables in the sauce for 20 minutes.
Heat oil in a pan and stir-fry the marinated beef and vegetables.
Once the beef is cooked, plate and serve.