In a medium, microwave-safe bowl, add peanut butter and maple syrup. Whisk together until well mixed.
Heat in 20-second increments in the microwave until warm and fragrant, and the mixture begins to dry out and become fluffy (about 4-7 rounds). Whisk in between heating increments. *Stovetop instructions in Notes.
Add coconut and oats. Stir and fold until thoroughly combined. Pour this mixture into the prepared baking pan. Using a rubber spatula, smooth into an even, tightly packed layer.