Sift or whisk 2 1/4 cups all-purpose flour, 1 1/2 tsp baking soda, 1 1/2 tsp baking powder and 1/4 tsp salt in mixing bowl.
In a large mixing bowl or bowl of a stand mixer, cream 1 1/2 cups unsalted butter and 3 cups brown sugar, packed until light and fluffy, about 2 minutes.
Add in 3 large eggs, beaten, zest of 1/2 lemon and 1 tsp lemon juice.
Slowly add in sifted dry ingredients, in three different additions. Fold in 4 cups old-fashioned oats.
Chill dough for minimum of 1 hour.
Using a small cookie scoop, scoop dough and roll into uniform balls of dough. Roll each ball of dough in granulated sugar and then powdered sugar. Place on cookie sheet (granulated sugar, for rolling and powdered sugar, for rolling can be placed in small, shallow bowls).
Bake at 375°F for 8-10 minutes, or until cookies have a crackled appearance and centers are set.