In a large bowl, mix 1 cup softened butter, 3/4 cups brown sugar, and 1/2 cup granulated sugar using an electric hand mixer.
Now mash up 2 bananas using a potato masher or a fork and add it to the butter mixture along with 2 eggs and 1 teaspoon vanilla extract. Beat that on medium speed until well combined.
Hold a fine-mesh sieve over the bowl of the banana and butter and add in 2 cups of all-purpose flour, 3/4 teaspoon baking soda, 1/2 teaspoon salt, 1 1/2 teaspoon cinnamon, and 1/4 teaspoon nutmeg. Then sift the dry ingredients in, and mix together at low speed.
Now add 3 cups of old-fashioned rolled oats along with 1 cup of semisweet chocolate chips. At this point mix everything together with a spatula.
At this point, you can round them balls in your hands or top with chocolate chips (optional). Now bake at 350 degrees Fahrenheit for 8-9 minutes.
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Notes
Don't have ripe bananas? No problem!If you don't have ripe bananas at home, you can ripen them in the oven! Place the unpeeled bananas on a parchment-lined baking sheet and bake at 300 degrees Fahrenheit for about 15-20 minutes.Can I freeze the cookie dough?Yes, this cookie dough can be frozen. If you want to make this banana oatmeal cookie dough ahead of time, go ahead and follow the recipe up to when you form the cookie balls. Instead of topping them with add-ins or baking, place them on the parchment-lined baking sheet and put it in the freezer for an hour. Once they are frozen, you can then put the cookie dough balls into a ziplock bag and keep them in the freezer for up to 3 months. Just take them out and bake them when you're ready.