Ensure that the cooked rice is cooled and not too sticky. It's ideal to use leftover rice from the refrigerator.
If using fresh vegetables, chop them into small, bite-sized pieces.
Heat a small skillet or wok over medium heat. Add the vegetable oil. Pour the beaten egg into the pan and scramble it until just cooked. Remove the scrambled egg from the pan and set it aside.
In the same pan, add a bit more oil if needed. Add minced garlic and stir-fry for about 30 seconds until aromatic. Add the mixed vegetables and stir-fry until they are tender yet still crisp.
Add the cooked rice to the pan and break up any clumps. Stir-fry the rice with the vegetables.
Return the scrambled egg to the pan and mix it into the rice and vegetables. In a small bowl, mix soy sauce and oyster sauce (if using). Pour the sauce over the rice and stir to combine.
Add chopped green onions and continue to stir-fry for another minute, ensuring everything is well combined.
Season the fried rice with salt and pepper according to your taste preferences.