Preheat your oven to 375 degrees Fahrenheit. It's essential to get your oven hot enough so that the cookies bake evenly and develop that perfect golden color.
In a large mixing bowl, beat the butter and both sugars together using an electric mixer until the mixture is smooth and creamy. This typically takes about 2 to 3 minutes. Look for a pale, fluffy texture that indicates the sugars have begun to dissolve.
Add in the egg and vanilla extract, mixing well until fully incorporated. The mixture should be smooth and glossy, reinforcing the creamy consistency from the butter.
In a separate bowl, combine the flour, baking powder, salt, and cinnamon. Stir these dry ingredients together, ensuring there are no lumps.
Gradually add the dry mixture to the wet ingredients, mixing on low speed. This will help prevent any flour from flying out of the bowl. You want to mix until just combined; over-mixing can lead to tougher cookies.
Now, fold in the rolled oats using a spatula. Make sure the oats are evenly distributed throughout the dough, as they provide that delightful chewy texture.
If your dough feels crumbly, add in 1 tablespoon of milk at a time until it starts to come together. Aim for a dough that holds its shape but isn’t too sticky.
Finally, gently fold in the chocolate chips. Make sure they're evenly distributed; every cookie should have a good amount of chocolate in it!
Once your dough is ready, refrigerate it for about 30 minutes. This helps the flavors meld and makes it easier to handle when forming balls.
After chilling, remove the dough from the fridge and roll it into 1 1/2 inch balls. Place them about 2 inches apart on a baking sheet lined with parchment paper.
Lightly press down on each cookie ball to flatten it slightly. Bake in the preheated oven for 9 to 11 minutes, or until the edges are just golden.
Once baked, remove the cookies from the oven and let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely. Enjoy your delicious Chewy Chocolate Chip Oatmeal Cookies!