1. Cut off leaves from radishes, leaving 1/2-inch stem on each, and trim root end. Cut each radish in half, or into quarters if they are very large. Cut yellow peppers into thin strips.
2. In 10-inch skillet over medium-high heat, in hot salad oil, cook radishes, yellow peppers, salt, and sage, stirring frequently, until vegetables are tender-crisp, about 5 to 8 minutes.