Line a baking sheet with parchment paper and preheat your oven to 350 degrees F.
Add the oats to a food processor and gently process until the oats are finely chopped, with some floury bits, but do not over process into flour.
Transfer the oats to a mixing bowl and add all remaining ingredients, except for your optional fill in. Mix well to evenly distribute. Now add your fill in of choice, if using and mix well.
Divide your cookie batter into 10 cookies, roll out a ball in your hands (use wet hands to prevent sticking) and then place down on your baking sheet. Now, using the back of a spoon, gently press each cookie down and shape the sides into a rounded cookie, if needed.
Bake for 10-12 minutes and remove from the oven. (They will look under done.) Let them cool for at least 5 minutes and then transfer to a cooling rack to cool for an additional 5-10 minutes to get your cookies to completely set and firm up. Enjoy!
Don't over process the oats. You don't want to make flour or this will alter the texture of your oatmeal cookies.Use wet hands to shape your cookie dough into balls. This will help prevent them from sticking to your hands, and make them easy to roll.When you press your cookies down, do so gently to prevent breaking them. Use your other hand to help shape the edges into a round cookie if they are not holding well at the edges.Don't use more than 1/4 cup of fill ins, whether it's chocolate chips, raisins or another fill in. Too much of any fill in will make them tougher to hold together.Do not over bake your cookies. For chewy oatmeal cookies, they should be slightly under baked. They may appear under done, but make sure not to over bake to prevent them from getting dry. Edges will be firmer and the center will be soft.Let them rest at room temperature for at least 5-10 minutes after baking. This brief cool down period will firm up your cookies and let them completely set.Cookies keep 2-3 days refrigerated, up to 1 week in the fridge, or freeze for up to 3 months.