Step 1

Preheat oven to 350°F. Grease a 9- x 5-inch loaf pan with 2 tablespoons butter. Coat pan with turbinado sugar, and tap out excess. Whisk together flour, cinnamon, salt, baking powder, baking soda, and allspice in a medium bowl; set aside.

Step 2

Whisk eggs in a large bowl until pale and foamy. Add zucchini, granulated sugar, oil, vanilla, and orange zest; whisk to combine. Add flour mixture, and whisk until just incorporated. Stir in pecans and 1/2 cup oats. Pour batter into prepared pan, and smooth top. Sprinkle with remaining 1 1/2 tablespoons oats.

Step 3

Bake in preheated oven until golden brown and a wooden pick inserted in center comes out clean, 55 minutes to 1 hour. Cool bread in pan on a wire rack 15 minutes. Remove bread from pan, and cool completely on wire rack, about 1 hour. Cut into slices, and serve with remaining 6 tablespoons softened butter.