Cream butter in a large mixing bowl. Gradually add sugar until light and fluffy. Beat in eggs.
In a separate bowl, combine flour, baking soda, salt, and cinnamon; add to butter mixture alternately with milk, beginning and ending with flour. Stir in oats, raisins and butterscotch chips.
Drop dough by tablespoonfuls 2 inches apart onto greased baking sheets or use parchment paper. Bake at 350 degrees F. for 12 minutes or until edges turn golden brown and tops are just set. Transfer to wire racks to cool completely.
Notes
Use room-temperature butter. Set it out on the counter about an hour before you need it. You'll be able to indent it with your finger but it should still feel cool to the touch.
I recommend using unsalted butter because salt is added to the recipe. If you only have salted butter, it's ok. Just cut down the amount of salt you add as an ingredient.
Old-fashioned rolled oats give the best texture, but if you're in a pinch, you can substitute quick oats. Just be aware the texture will be slightly different.
Remove the cookies from the oven when the edges begin to brown and the tops are just set. They may look underdone, but you don't want to overbake them. We want them soft and chewy; they'll finish setting up as they cool.
If butterscotch isn't your thing, use chocolate chips instead. AND if you don't love raisins, you can leave them out.