Heat oven to 350°F. Line 2 baking sheets with parchment paper.
In a large bowl, cream the ½ cup unsalted butter until fluffy. Add ⅔ cup maple syrup and beat until well incorporated; add the 1 egg and beat well to combine.
In a food processor, grind 1 ¼ cups of the 3 ¼ cups rolled oats until fine. Place in a medium bowl and stir in the ½ teaspoon baking powder, ½ teaspoon baking soda, and ½ teaspoon fine sea salt.
Add dry mixture to wet mixture and stir to combine. Add the 2 cups whole rolled oats and the 1 cup semisweet chocolate chips. Stir to incorporate.
With a teaspoon or a cookie scoop, scoop out balls of dough; mixture will be wet. Roll in your hands to form a ball and place 1-inch apart on the cookie sheets. Bake for about 15 minutes until cookies are set and lightly browned. Remove from oven and let cool 2 minutes on baking sheet, then transfer to a wire rack to cool completely.