1 1/4 cup (2.5 sticks) butter 1 cup brown sugar, packed 1/2 cup sugar 1 large egg 1 tablespoon vanilla extract 1 1/2 cups all-purpose flour 1 teaspoon baking soda 1/2 teaspoon salt 1/2 teaspoon cinnamon 3 cups quick oats 1. Preheat the oven to 350 degrees F. With an electric mixer, beat the butter