Heat the vegetable oil in a large skillet over medium heat. Crack the eggs into the skillet and scramble them until just set, then push them to one side.
Add the frozen mixed vegetables to the empty side of the skillet. Cook for 3 to 4 minutes, stirring occasionally, until the vegetables are warmed through.
Add the cooked rice to the skillet along with the soy sauce, salt, and black pepper. Stir everything together so the rice and vegetables are evenly coated.
Cook for another 4 to 5 minutes, stirring now and then, until the rice is heated and starts to pick up a bit of color.
Stir in the sliced green onions and remove the skillet from the heat.