Preheat oven to 350 degrees F (175 degrees C). Lightly grease a 9×5 inch loaf pan. In a small bowl, mix together 1/3 cup sugar and 2 teaspoons cinnamon; set aside.
In large bowl combine flour, baking powder, salt and remaining 1 cup sugar. Combine egg, milk, and oil; add to flour mixture. Stir until just moistened.
Pour half of the batter into pan. Sprinkle with half the reserved cinnamon/sugar mixture. Repeat with remaining batter and cinnamon/sugar mixture. Draw a knife through batter to marble.
Bake in preheated oven for 45 to 50 minutes, or until a toothpick inserted into center of the loaf comes out clean. Let cool in pan for 10 minutes before removing to a wire rack to cool completely. Wrap in foil and let sit overnight before slicing.