Preheat oven to 250 F (120 C). Line a baking sheet with parchment paper or non-stick aluminum foil (or spray foil with cooking spray). Set aside.
Combine the oats, wheat bran, oat bran, sunflower seeds, and pecans in a large heatproof bowl.
3¼ cups rolled oats, ½ cup wheat bran, ½ cup oat bran, ⅓ cup sunflower seeds, ⅓ cup pecans
In a small saucepan, combine the maple syrup, oil, cinnamon, vanilla extract, and salt. Bring to a boil over medium heat.
½ cup maple syrup, ⅓ cup vegetable oil, 2 tablespoons ground cinnamon, 1½ teaspoon vanilla extract, ½ teaspoon salt
Immediately pour liquid mixture over dry ingredients and stir to coat.
Spread the mixture evenly on the baking sheet. Bake until crispy and toasted, about 45-50 minutes.
Remove from oven and allow to cool. Crumble into a large bowl, leaving large chunks, and carefully stir in raisins, if using.
¾ cup raisins