Break the cold rice into loose grains with clean fingers or a fork. Brown the beef in a large skillet over medium-high heat for 6 to 7 minutes, cooking it to 160°F; transfer to a bowl and drain excess fat.
Add 1 teaspoon neutral oil and scramble the beaten eggs for 1 minute until fully set. Transfer them to the beef bowl.
Add the remaining neutral oil, scallion whites, garlic and frozen vegetables. Stir-fry for 2 minutes, then add the rice and press it into a broad layer.
Cook for 3 to 4 minutes, turning every minute, until the rice is hot throughout. Return the beef and eggs, add soy sauce, oyster sauce, sesame oil and white pepper and toss until the mixture reaches 165°F.
Fold in the scallion greens and divide among four bowls. Refrigerate any leftovers promptly.