In a medium bowl, whisk together the 1 ½ cups whole wheat flour or oat flour, 1 teaspoon baking soda, and ½ teaspoon fine sea salt.
In a large bowl using a hand mixer, beat the 1 cup unsalted butter, 1 cup light or dark brown sugar, and ½ cup granulated sugar on medium-high speed until combined and fluffy about 3 minutes. Add the 2 large eggs and 2 teaspoons pure vanilla extract and beat until combined.
Add the dry ingredients to the wet ingredients and mix on low speed until combined. Beat in the 3 cups old-fashioned rolled oats and 1 ½ cups semi-sweet chocolate chips.
Cover and transfer the dough to the refrigerator to chill for at least 45 minutes (and up to 3 days).
Preheat oven to 350°F. Line 2 baking sheets with parchment paper.
Scoop out cookies (try 1-2 tablespoons' worth of dough depending on how large you want them), place on the trays about 1 inch apart, and bake for 13–15 minutes until set and lightly browned
Remove from the oven and allow the cookies to cool on the baking sheet for 5 minutes before transferring to a cooling rack to cool completely.
Notes
Bring butter to room temperature first. For the smoothest dough that bakes into the tenderest cookies, bring the butter to room temperature on the counter (I like my butter to be easily pressed with a finger). Then, continue with the recipe.
Brown the butter. For an undertone of nutty, caramelized flavor, brown the butter! If you do brown the butter first, let the butter cool a bit, then proceed with the recipe. You can still use an electric mixer to make the dough, or, since the butter is melted, you can use a whisk and a spoon to make the dough.
Go gluten-free. Keep it easy, and use oat flour (or another whole grain gluten-free flour) for the whole wheat flour. Or, use an all-purpose gluten-free blend, like my homemade gluten free flour blend.
Add a little spice. Whisk in ½ teaspoon of ground cinnamon to the flour mix for a little warmth.
Adjust the bake time. If you like an underdone, softer cookie, bake the cookies a minute or so less. Make sure to let the cookies set and cool on the baking tray so that they don't fall apart.
Refined sugar-free - Substitute coconut sugar for the brown sugar and granulated sugar, or use a mix of maple sugar and coconut sugar.