In a mixing bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar, brown sugar, baking soda, and salt. Beat until combined, scraping bowl occasionally. Beat in egg and vanilla until combined. Beat in flour until combined. Stir in rolled oats, pretzels, and raisins. Cover and chill dough about 1 hour or until easy to handle.
Preheat oven to 375 degrees F. Roll dough into 1-inch balls. Place balls 2 inches apart on an ungreased cookie sheet. Flatten balls slightly.
Bake for 7 to 8 minutes or until edges are browned. Transfer to a wire rack and let cool.