Preheat oven to 350 degrees F.
In medium size bowl, add flour, baking powder, salt, and cinnamon. Stir the dry ingredients together and set aside.
In a large mixing bowl, add the butter, sugar, brown sugar, egg and vanilla extract. Beat until light and fluffy.
Turn the mixer speed to low and slowly add the flour mixture. Once incorporated, turn the mixer to a higher speed until a dough forms.
Using a spatula or large spoon, stir in the oatmeal, dried blueberries, and peanut butter chips.
Grease a cookie sheet with butter. Add all of the cookie dough onto the baking sheet.
Using a rubber spatula or large spoon, gently spread the cookie dough out evenly over the entire bottom of the cookie sheet. Keep the dough about 1/8th of an inch away from all sides of the sheet.
Bake in a preheated oven for about 19 to 20 minutes. Remove the pan from the oven when the dough in the middle of the pan is still slightly soft.
Let the pan sit on a rack to cool. It should continue to cook a bit more in the middle of the pan from the residual heat.
After 20 minutes, use a large pizza cutter or knife to cut the cookie into bars. Carefully remove the cookie bars from the pan onto a rack to cool further.
Serve once the cookie bars have cooled.