Preheat the oven to 350?F. Grease a 9 x 13-inch casserole with the oil and set aside.
Bring a large pot of water to a boil, add the carrots, and cook until tender, about 15 minutes; drain. Combine the carrots with the remaining ingredients in a food processor and process until smooth, scraping down the sides of the bowl as necessary.
Spoon the mixture into the prepared casserole.
Combine the brown sugar, pecans, flour, and butter in a medium bowl. Stir to blend. Scatter the mixture over the top of the casserole and bake until the topping is lightly browned, 55 minutes to 1 hour.
Makes 10 to 12 servings