In a large bowl combine the oats, milk and brown sugar and let stand for at least 1 hour. Don't skip this step or shorten the time. If you don't, they won't turn out as well. If you know that you want to bake the muffins in the morning, you could do this step the evening before and let is set overnight.
Preheat the oven to 400°F.
Get muffin pan out. The muffin pan that I use makes 8 larger muffins or 12 regular sized muffins.
Mix dry ingredients (flour, baking powder, baking soda, cinnamon and salt) together in a separate bowl.
Add other wet ingredients (melted butter, eggs, vanilla) to the oats, milk, brown sugar mixture and combine.
Add the dry mixture to the wet mixture. Stir until just combined and add the butterscotch chips.
Make sure that your muffin pan is either greased or lined with muffin liners.
Scoop batter in into muffin pan and bake for about 30 minutes. Check to make sure that a toothpick inserted into the center of a muffin comes out clean.
Let cool a few minutes and remove muffins from pan.
Lastly, enjoy. They do keep pretty well in an airtight container for a few days.