1. In a bowl, combine soy sauce, sesame oil, brown sugar, and garlic. Set aside.

2. Heat vegetable oil in a large skillet or wok over high heat.

3. Add thinly sliced beef to the skillet and cook until browned. Remove from skillet and set aside.

4. In the same skillet, add chopped bell peppers, broccoli florets, and sliced carrots. Cook until vegetables are crisp-tender.

5. Return the cooked beef to the skillet with the vegetables.

6. Pour the soy sauce mixture over the beef and vegetables. Stir well to coat everything in the sauce.

7. Cook for an additional 2-3 minutes, until heated through.

8. Serve hot with steamed rice or noodles.