Mix flour, pecans, sugar, butter, and 1/2 toffee bits in large bowl. Mix and press in bottom of a 9 x 13 inch pan. Bake at 400 degrees for 10 minutes. Cool.
Pour milk into large bowl. Add pudding mix, beat with whisk for 2 minutes. Spread 1 1/2 cups pudding mix on bottom of crust. Gently stir 1/2 whipped topping into remaining pudding. Spread over pudding in pan. Top with remaining whipped topping. Sprinkle with remaining toffee bits. Refrigerate for 3 hours or overnight.