Heat vegetable oil in a wok or large skillet over medium heat. Add corned beef; cook and stir until heated through, about 3 minutes. Add spinach; cook and stir until wilted, about 2 minutes.
Push beef and spinach to the sides of the work; pour eggs into the center; cook, stirring frequently, until eggs are scrambled, about 3 minutes. Stir in rice; cook until heated through, about 5 minutes. Season with garlic powder and salt.