I personally like the granola bars without the peanut butter addition, but if you find them a bit on the dry side (which I like), feel free to add it in to the mix. They are also delicious with some peanut butter slathered on top!
Preheat oven to 350 degrees and spread oats, chopped pecans, pumpkin seeds, and walnuts on a parchment lined baking sheet. Place in oven and bake until lightly toasted, about 10 minutes.
In a medium bowl, mash bananas. Stir in apple sauce and peanut butter (if using) until combined.
Place the toasted oat and nut mixture in a large bowl and add in the dried cranberries, ground flax seed, cinnamon, and salt and stir until combined.
Stir the banana mixture into the oat mixture until well combined and starting to form clumps.
Meanwhile, prepare a 9 x 13 baking dish with parchment paper, letting the parchment paper overlap all sides by about 1 inch.
Transfer the oat mixture into the prepared baking dish and press down mixture evenly into pan.
Bake until the bars are golden and start to pull away from the sides of the baking dish, about 30 minutes. Let cool for at least 15 minutes.
Using the parchment paper, lift bars from pan and let them completely cool to room temperature. Cut into 16 bars and store in airtight container or wrap individually and place in the freezer.