Pre-heat oven to 350 degrees F. In a small bowl, combine the flour, oats and brown sugar. Cut in butter until mixture is crumbly. Press into a greased 13-in. x 9-in. baking pan. Bake for 20 minutes or until golden brown. In a large bowl, beat filling ingredients until smooth; pour over crust. Bake for 45 minutes or until a knife inserted near the center comes out clean. Let cool completely. While that's cooling, prepare the pudding according to package directions (careful to use only 1-1/2 cups of milk, rather than 2 cups). Let chill in fridge for at least 1 hour. Spread on top of brownies and sprinkle cinnamon on top.
Recipe by Thrifty DIY Diva at https://www.thriftydiydiva.com/pumpkin-pie-pudding-brownies/