Preheat oven to 350 degrees. Butter three 8 or 9 inch cake pans and flour or line with parchment paper.
Add the cake mix, oil and eggs and mix on low until blended. Reserve a couple of the orange slices for garnish if desired. Add the remaining oranges with their juice, blend on low for about 2 minutes. Divide evenly among pan and bake for 20-25 minutes, then turn out into a cake rack to cool completely.