Preheat oven to 350 degrees F (175 degrees C). Once oven reaches desired temperature, melt margarine in a glass 9×13 baking pan.
In a large bowl, combine flour, sugar and baking powder. Pour reserved peach juice into dry ingredients and stir until smooth. Remove glass pan from oven and pour batter in starting in the center; batter will then spread itself over entire pan. Add peaches by placing them in center of pan; allow them to spread on their own.
Bake cobbler in preheated oven for 20 to 25 minutes, or until brown on top. Do not overcook.