Preheat the oven to 325 degrees F (165 degrees C).

Cream butter, brown sugar, and white sugar in a large bowl with an electric mixer until fluffy. Beat in one egg at a time, then stir in vanilla.

Combine flour, cinnamon, salt, and baking soda in a separate bowl; stir into the creamed mixture. Mix in oats and walnuts until just blended. Drop teaspoonfuls of dough 2 inches apart onto ungreased cookie sheets.

Bake in the preheated oven until edges are golden, about 12 minutes. Transfer to a wire rack to cool.