Step 1: Preheat the Oven - Begin by preheating your oven to 350°F (175°C). This ensures that your oatmeal squares bake evenly and come out perfectly golden.
Step 2: Prepare Your Baking Pan - Line your 9x13-inch baking pan with parchment paper, leaving some overhang for easy removal later.
Step 3: Cream the Coconut Oil and Sugar - In a large mixing bowl, combine the coconut oil and packed coconut sugar. Mix until creamy.
Step 4: Add Dry Ingredients - Add the whole wheat pastry flour, old-fashioned oats, baking soda, and salt. Stir until well incorporated.
Step 5: Fold in Marshmallows and Chocolate Chips - Gently fold in mini marshmallows and chocolate chips. The batter will be thick and sticky.
Step 6: Spread the Batter - Spread the batter evenly into the prepared baking pan.
Step 7: Bake - Place the baking pan in the preheated oven and bake for 25-30 minutes, or until golden brown.
Step 8: Cool and Cut - Allow to cool in the pan for about 10 minutes, then cool completely on a wire rack. Cut into squares and serve!