Preheat oven to 350 degrees F.

Combine brown sugar, oil and beaten egg. In a small bowl mix together buttermilk, baking soda, salt, and vanilla. Add milk mixture to sugar mixture alternately with flour, beating well after each addition. Fold in rhubarb and pecans.

Turn into 2 greased and floured 8 x 4 x 3-inch loaf pans. Mix topping ingredients and sprinkle on top of loaves.

Bake about 1 hour or until toothpick inserted center of bread comes out clean.