Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper or a silicone mat.

In a large bowl, cream the softened butter with the brown sugar and granulated sugar until smooth and slightly fluffy, using a hand mixer for about 2–3 minutes.

Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

In a separate bowl, whisk together the all-purpose flour, baking soda, and salt. Gradually add the dry mixture to the creamed butter-sugar mixture and mix until combined.

Fold in the rolled oats and butterscotch chips with a spatula until evenly distributed.

Drop rounded tablespoons of dough about 2 inches apart on the prepared baking sheets.

Bake for 10–12 minutes, until the edges are set and lightly golden, with the centers slightly underbaked.

Let the cookies cool on the baking sheets for 3–5 minutes, then transfer to wire racks to cool completely.