Preheat oven to 350 degrees F. Line two cookie sheets with parchment paper.

Remove 1 teaspoon of flour from the 1 cup measure and set aside. Mix the remaining flour, cinnamon, salt, baking soda and baking powder together in a bowl; set aside.

Beat the butter and brown sugar using high speed of an electric mixer until creamy. Beat in the vanilla, then add the egg and beat just until incorporated. Gradually add the flour mixture to batter, stirring just until absorbed. Then stir in oats and walnuts. Toss the frozen blueberries in the reserved teaspoon of flour and stir in the blueberries

Carefully shape into balls (mine were a little over an inch) and space about 2 ½ inches apart on the parchment lined cookie sheets.

Bake at 350 degrees for 12-15 minutes (check at 10). Let cool on cookie sheets for about 3 minutes, then transfer to a wire rack to cool.