Heat the oil in a wok or large skillet over medium heat. Add the chopped onions and sauté for 2 minutes until they turn translucent and smell sweet.
Add the finely chopped carrot and bell pepper to the pan. Stir-fry for 2–3 minutes. You want them to soften slightly but still keep a bit of their Toss in the diced tomato and cook for just 30 seconds. Chef’s Note: Do not overcook the tomatoes, or they will turn into mush and make the rice soggy.
Add the cooked rice to the pan. Sprinkle evenly with salt, black pepper, and dried oregano.
Toss everything together vigorously, breaking up any clumps of rice, until the grains are hot and evenly coated with the seasoned oil and vegetables. Serve immediately.