Add apples to a large microwave-safe mixing bowl. Heat apples in microwave in 15-20 second intervals, stirring in between until they are just starting to cook. This should take less than a minute (mine took 40 seconds). You want the apples to be still crisp, but they should change color and start releasing some liquid. Do not heat more than 15-20 seconds at a time because you can burn the apples.
Add in the peanut butter and stir with a spatula until fully incorporated. The peanut butter should turn from liquidy to stiff and thick, almost like a cookie dough consistency.
Once the dough is thick, use a whisk to mash the apples in. The apples do not need to be fully mashed. The goal is to release some more of the apple juices into the peanut butter and make the apple pieces a little smaller (about half of the size they started out as).
Add in the quick oats. Use a spatula to mix them into the dough until the oats are fully incorporated.
Using a 1 tbsp cookie scoop, scoop out dough balls and place onto the cookie sheet, spacing the balls about 1 inch apart. Press down on each dough ball with the back of a metal spoon until it forms a round disk (about 1/2 inch thick). Cookies will not change shape so shape them as you would like your final cookies to be. You can use your fingers to smooth the edges.
Place cookies into fridge for about 30 minutes to one hour to firm up. The cookies will not change much but they will be firmer, making them easier to hold and eat. Store uneaten cookies in the fridge.
Notes
Make sure to use a sweet and crisp apple type. Something like Fuji, Ambrosia or Honey Crisp.
Make sure to core and peel the apples before cutting them into 1/2 inch by 1/4 inch pieces.
You must use natural peanut butter (no oils added). This recipe will not work with regular peanut butter (that has oils added). See post for substitutions.
The cookies are only lightly sweetened with the apples and have no additional sugar. If you prefer your cookies to be sweeter you can add chocolate chips or sprinkle some sugar on top.
You can also add cinnamon for more flavor (add 1/2 tsp into the dough).
Cooking the apples in the microwave slightly will help the apples release some of their juices, make it easier to incorporate the apple flavor into the dough and also will give the cookies more of a baked apple cookie taste.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.