Preheat oven to 375 F. Line baking sheets with parchment paper or silicone baking mats. Set aside.
Melt butter in a small saucepan over medium-high heat, stirring occasionally, until the butter turns amber brown and smells nutty, about 2 minutes.
Pour the butter and any browned bits into a large, heatproof bowl.
Stir in the brown sugar, granulated sugar, and oil until combined.
Add the egg, egg yolk, and vanilla. Whisk in until combined.
Add flour, salt, baking soda, and cinnamon. Stir in just until combined.
Stir in oats and raisins.
Scoop dough by 1.5 tablespoon (medium cookie scoop) and place dough scoops 2 inches apart on prepared baking sheet.
Gently press the dough down slightly.
Bake 7-10 minutes, or until the edges of the cookies are set and the centers are soft.
Let cookies cool on sheet for 5 minutes.
Transfer to a wire cooling rack to cool completely.
Notes
You can use light brown sugar, but the flavor won't be quite as strong.
I highly recommend weighing the flour. If you don't have a kitchen scale, sift or stir the flour to break it up. Lightly spoon it into the measuring cup (don't scoop it) and then level.
You can substitute other types of dried fruit, like cranberries, or chocolate chips.