Preheat your oven to 350°F (175°C). Grease or line a 9x13-inch baking pan with parchment paper for easy removal.
In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
In a separate bowl, whisk together the all-purpose flour, baking soda, ground cinnamon, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Stir in the rolled oats and raisins until evenly distributed throughout the dough.
Spread the mixture evenly in the prepared baking pan, smoothing the top with a spatula.
Bake in the preheated oven for 25 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out clean.
Allow to cool in the pan for about 10 minutes before transferring to a wire rack to cool completely. Once cooled, cut into 12 bars.