Preheat oven to 325 degrees F.
In a large bowl with a spatula, or stand mixer with the paddle attachment, cream together the butter, sugar, and brown sugar until light and fluffy, or about 3-4 minutes.
Add the lemon juice, vanilla, salt and cinnamon and mix to combine, then add the eggs one at a time, scraping down the sides after each addition.
In a separate medium bowl, combine the flour, rolled oats and baking soda and whisk well, then add the flour mixture into the butter mixture and mix until just combined. You may want to scrape the bottom and sides of the mixing bowl to be sure all of the ingredients are incorporate.
Add chocolate chips and walnuts and mix gently, just until all ingredients are combined.
Line baking sheets with parchment paper, or grease lightly with pan spray, then scoop and roll 1¼" balls and place on the prepared trays.
Bake in a preheated oven for 10-12 minutes, or until the edges are golden brown, but the center is still soft.
Remove from oven and let the cookies cool on the pan for about 2 minutes before transferring them to a wire rack to cool completely. Enjoy!