Preheat oven to 300 degrees F. Line a cookie sheet with parchment paper.
Add the butter, granulated sugar, and brown sugar in a large bowl. Beat with a hand mixer on medium for 3 minutes until light and fluffy.
Add the eggs, vanilla, and lemon juice. Beat on low until the eggs are incorporated and then turn mixer to medium and continue to beat for an additional 2 minutes until light and fluffy.
Add the flour, oats, baking soda, salt, and cinnamon. Beat just until the dry ingredients are worked into the dough.
Stir in chocolate chips and walnuts until evenly distributed.
Scoop the cookies with a 3 tablespoon cookie scoop onto the prepared cookie sheet about 2 inches apart.
Bake for 20 to 23 minutes or until edges are golden brown and center is still soft.
Remove from the oven and let cool for 10 minutes before transferring to a wire rack.
Store in an airtight container at room temperature.
Notes
I used 1 cup of chopped walnuts and ¾ cup of chopped pecans.