Preheat the oven to 350°F (175°C). Line an 8×8-inch baking pan with parchment paper, leaving an overhang on the sides for easy removal.
In a large mixing bowl, combine the rolled oats, whole wheat flour, chopped walnuts, dried cranberries, ground flaxseed, baking powder, ground cinnamon, and salt. Stir until evenly mixed.
In a separate medium bowl, whisk together the unsweetened applesauce, honey, melted coconut oil, eggs, and pure vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients. Stir with a spatula until just combined and all ingredients are evenly incorporated.
Transfer the batter to the prepared baking pan. Use the back of a spatula or your hands to press the mixture firmly and evenly into the pan.
Bake in the preheated oven for 22 to 25 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out clean.
Remove the pan from the oven and allow the bars to cool completely in the pan on a wire rack.
Once cooled, use the parchment paper overhang to lift the bars out of the pan. Place on a cutting board and cut into 12 equal bars.
To freeze, wrap each bar individually in plastic wrap or aluminum foil, then place them in an airtight freezer-safe container or resealable freezer bag.
To serve, thaw bars at room temperature for 30 minutes or microwave for 20-30 seconds until warmed.