Heat 1 tablespoon vegetable oil in a large skillet or wok over medium-high heat.
Add diced onion and carrots; cook for 3-4 minutes until they begin to soften.
Stir in peas and garlic; cook for 1 minute until fragrant.
Push vegetables to the side of the skillet, add remaining oil, and pour in the beaten eggs.
Scramble the eggs until just set, then mix them into the vegetables.
Add the cooked rice, breaking up any clumps, and stir-fry for 3-4 minutes.
Pour in soy sauce, oyster sauce (if using), and sesame oil; toss to combine.
Season with salt and pepper to taste.
Garnish with sliced green onions before serving.