Lay bread slices on two or three large baking sheets lined with parchment paper, set aside.
Allow bread to air dry 24 to 48 hours.
Turn bread slices over, frequently. Continue to allow the bread to dry out.
Butter a 8 x 8 x 2 inch baking dish.
In a medium bowl, mix together the cornbread muffin mix, milk and egg.
Mix just until moistened. Spoon into buttered dish.
Bake according to directions an box. Remove form oven and cool on wire rack for 10 minutes.
Remove cornbread from pan and break in half.
Place cornbread on another baking sheet lined with parchment paper. Allow to dry out overnight.
Remove thawed turkey from outer package. Rinse under running cold water.
Remove neck, liver, heart and gizzards from inside of turkey.
Set aside heart and liver for the stuffing.
Save neck and gizzards for another recipe or freeze for stock.
Set turkey aside. Remove oven bag from package.
Place flour inside oven bag, shake flour around in oven bag, discard excess flour, set aside.
Make stuffing: In a large skillet melt butter over medium low heat.
Add chopped onion, celery, liver and heart. Cook 10 minutes or until celery is tender.
Add poultry seasoning, sage, salt and pepper. Cook 3 minutes. Remove from heat, set aside.
With a serrated knife, cut bread and cornbread into 2 inch cubes.
Place bread cubes into a large bowl. Add beaten egg and onion mixture.
Mix together well, using your hands for the best results.
Add a small amount of turkey broth or stock at a time,
mixing well after each addition, until bread mixture is moistened but not soggy.
Stuff turkey and neck cavity with dressing. Drizzle turkey with vegetable oil, lightly massage into the skin.
Place stuffed turkey into the prepared oven bag.
Use twist tie to close the oven bag.
Make 4 small slits in the top of the oven bag.
Roast turkey according to oven bag directions.