Preheat Oven: Preheat your oven to 300°F (150°C). Grease two 8 1/2 x 4 1/2-inch loaf pans with cooking spray or butter.
Prepare Dry Ingredients: In a large bowl, combine the flour, baking soda, salt, chopped walnuts (if using), and ground cinnamon. Mix well to ensure even distribution.
Add Apples: Fold the chopped apples into the dry ingredient mixture, ensuring they are well coated.
Combine Wet Ingredients: In a separate bowl, whisk together the vegetable oil, granulated sugar, beaten eggs, and vanilla extract until fully combined.
Pour the liquid mixture into the dry ingredients to combine them. Stir gently until just moistened; avoid overmixing to prevent a dense loaf.
Divide Batter: Using a spatula to smooth the tops, divide the batter evenly between the two loaf pans that have been prepped.
Bake: Place the pans in the preheated oven and bake for approximately 90 minutes, or until a toothpick inserted into the center of the loaves comes out clean.
Cool: Take the pans out of the oven and give the loaves ten minutes or so to cool in the pans. Then, place the loaves on a wire rack to cool entirely before slicing.