1. Remove the stone from the peach or nectarine and cut the fruit into bite-size pieces with a sharp knife.
2. Divide the chopped fruit between two tall glasses, reserving a few pieces for decoration.
3. Sprinkle the oat cereal over the fruit in an even layer, then top with the low fat yogurt.
4. Stir the jam and the fruit juice together in a jug, then drizzle the mixture over the yogurt. Decorate with the reserved peach or nectarine pieces and serve at once.