Spread oats and walnuts on a baking sheet. Bake at 375° for 8 minutes or until lightly browned, stirring occasionally. Remove to wire racks to cool.
In a large bowl, combine the flour, sugar, baking powder, salt and oat mixture. Cut in butter until mixture resembles coarse crumbs. In a small bowl, whisk the maple syrup, milk, cream, egg and vanilla; stir into crumb mixture just until moistened. (Dough will be soft.) Stir in chips.
Transfer dough to a greased baking sheet. Pat into a 7-in. circle. Cut into eight wedges, but do not separate. Cover and refrigerate overnight. Bake at 400° for 25-30 minutes or until golden brown.