Preheat the oven to 350F. In a large bowl, beat the butter, sugar, oil, eggs and vanilla with an electric mixer for 2-3 minutes, until pale yellow and fluffy. Add the eggs and vanilla and beat well.

In a small bowl, stir together the flour, baking powder, baking soda, cinnamon, nutmeg, allspice and salt. Add about a third to the butter mixture and beat on low speed just until blended. Add half the grated pears and half the buttermilk, then another third of the flour, the rest of the pears and buttermilk and the rest of the flour, stirring or beating on low speed just until combined.

Gently stir in the raisins or cranberries and scrape the batter into two 8-x 4-inch loaf pans that have been sprayed with nonstick spray. Bake for 50-60 minutes, until golden and tops are springy to the touch. Cool completely in their pans on a wire rack.