Preheat oven to 325 degrees F.
Coat a large, rimmed baking sheet with nonstick cooking spray. (I greased my pan with butter)
Stir oats, syrup, walnuts, oil, and salt in a large mixing bowl.
Spread mixture onto the prepared baking sheet.
Transfer pan to the oven and bake for 45 minutes.
Remove baking sheet from the oven, stir mixture gently, and return to the oven for another 10 minutes.
Turn off the oven, but do not open the door.
Let granola sit in the warm oven for 20-25 minutes, until crisp and golden.
Remove granola from oven.
Let granola cook on the baking sheet.
Stir in cranberries.
Store in an airtight container for up to 2 weeks.