Preheat oven to 350 degrees.  Line baking sheets with parchment paper.

In a large bowl, beat butter and brown sugar at medium speed with an electric mixer until creamy.  Add egg and milk, beating to combine well.

In a medium bowl, combine flour, baking soda, and salt; gradually add to butter mixture, beating until combined.  Stir in oats, cranberries, and white chocolate morsels.  Drop batter by rounded tablespoonfuls onto prepared baking sheets.  Bake for 12 to 14 minutes, or until lightly browned.  Let cool for 2 minutes on baking sheets; remove to wire racks and cool completely.