Heat 1 tablespoon vegetable oil in a large skillet or wok over medium-high heat. Add diced chicken, season with salt and pepper, and cook until fully cooked. Remove and set aside.

In the same skillet, add remaining oil and sauté garlic and onion until fragrant.

Push garlic and onion to the side, pour in beaten eggs, and scramble until just set.

Add cooked rice to the skillet, breaking up any clumps. Stir-fry for 2–3 minutes until heated through.

Return cooked chicken to the skillet and add mixed vegetables. Stir to combine.

Add soy sauce, oyster sauce (if using), and sesame oil. Toss everything together until evenly coated and heated.

Adjust seasoning with salt and pepper. Garnish with sliced green onions and serve hot.