Prep your tools: Heat the oven to 350°F (175°C). Line two baking sheets with parchment paper. This prevents sticking and helps even browning.

Cream the butter and sugars: In a large bowl, beat 1 cup softened unsalted butter with 1 cup packed brown sugar and 1/2 cup granulated sugar until light and fluffy, about 2–3 minutes. This step adds air and creates a tender cookie.

Add eggs and vanilla: Beat in 2 large eggs, one at a time, then mix in 2 teaspoons vanilla extract. Scrape down the bowl so everything is well combined.

Mix dry ingredients: In a separate bowl, whisk together 1 1/2 cups all-purpose flour, 1 teaspoon baking soda, 1 teaspoon ground cinnamon, and 1/2 teaspoon salt.

Combine wet and dry: Add the dry mixture to the butter mixture and mix on low just until the flour disappears. Don’t overmix or the cookies can turn tough.

Fold in oats and raisins: Stir in 3 cups old-fashioned oats and 1 1/2 cups raisins. The dough will be thick and slightly sticky. If using nuts or chocolate chips, fold in up to 3/4 cup now.

Optional chill: For thicker cookies, chill the dough for 20–30 minutes. If you prefer thinner, chewier cookies, bake right away.

Scoop and space: Scoop heaping tablespoonfuls (or use a 1.5-tablespoon cookie scoop) onto the prepared sheets, spacing about 2 inches apart.

Bake: Bake 10–12 minutes, until edges are set and lightly golden but centers still look slightly underdone. They’ll finish setting as they cool.

Cool: Let cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely. This helps them stay chewy.