Preheat the oven to 350°F. Line 2 baking sheets with parchment paper.
Sift together the all-purpose flour, baking powder, salt and baking soda. Set aside.
In the bowl of a stand mixer, cream together the softened butter, light brown sugar, granulated sugar, peanut butter and vanilla. Beat for 3 minutes until smooth, fluffy and light beige in color. Add the eggs one at a time beating well after each addition. Stop to scrape the bowl periodically so all of the ingredients fully combine.
Add the dry ingredients gradually while beating on low speed, mixing well between each addition.
Repeat until all of the dry ingredients have been added, stopping to scrape the sides of the bowl as needed.
After all of the dry ingredients have been added, increase the speed of the mixer and beat for 1 minute.
Use a large non-stick spatula to mix in the quick-cooking oats, peanuts, milk chocolate chips and sweetened flaked coconut by hand. The batter will be stiff.
Use a 4 oz ice cream scoop to separate the dough. Place the dough rounds at least 3-inches apart on the baking sheet. Press the centers to flatten slightly for even baking.
Bake for 16-18 minutes until lightly golden.
Cool on the cookie sheet for 5 minutes, then remove to a cooling rack to cool completely.
A 4 oz ice cream scoop will yield jumbo cookies. If you choose to make these cookies smaller, decrease the baking time accordingly.