In a bowl, toss sliced beef with soy sauce, cornstarch, and sesame oil. Let it marinate for 10–15 minutes while prepping the other ingredients.
Heat a wok or large skillet over medium heat. Add a small amount of oil, then pour in the beaten eggs. Scramble until just set. Remove and set aside.
Add a tablespoon of oil to the skillet. Add the marinated beef in a single layer and sear until browned and just cooked through, about 2–3 minutes. Remove and set aside.
Add garlic, peas, and carrots to the skillet. Sauté for 2–3 minutes until warmed through and fragrant.
Add the cold rice to the skillet. Use a spatula to break up clumps and mix it into the veggies. Stir in soy sauce, oyster sauce (if using), and sesame oil. Cook for another 2–3 minutes, letting the rice get a little crispy on the bottom.
Return the cooked beef and scrambled eggs to the pan. Stir everything together until heated through. Add chopped green onions and season with salt and pepper as needed.
Dish up while hot and serve as a main course or alongside other Asian-inspired dishes.