Melt the margarine in a large saucepan over medium heat. Cook and stir the apples and pears in the melted margarine for about 5 minutes.
Add the vegetable stock, sage, pepper and bay leaf to the saucepan; bring to a boil. Reduce heat to low. Place a cover on the saucepan and allow the mixture to simmer until hot and the apples and pears are tender, about 20 minutes. Remove from heat and allow to cool for 5 minutes.
Pour about 1/3 of the soup into a blender filling the pitcher no more than halfway full. Hold the lid of the blender in place with a towel and carefully start the blender using a few quick pulses to get the soup moving before leaving it on to puree. Puree in batches until smooth; pour into a clean saucepan. Alternately, you can use a stick blender and puree the soup right in the saucepan.
Return the pureed soup to the saucepan and warm over medium heat until completely reheated. Garnish with parsley to serve.