Heat oven to 350ºF. Grease or spray 13x9-inch baking dish.
In large bowl, beat sweet potatoes and pumpkin with electric mixer on medium speed until smooth. Add sugar, cinnamon and vanilla. Beat until well mixed. Beat in milk and eggs. Spread evenly in baking dish.
In large bowl, mix cookie dough, oats and flour, crumbling into small pieces. Sprinkle on top of sweet potato mixture. Top with pecans.
Bake 45 to 50 minutes or until top is golden brown and filling is set. Immediately top with miniature chocolate chips. Cool 15 minutes before serving. Serve with whipped topping and nutmeg, if desired.