Preheat the oven to 350 degrees F and position the oven rack one level below the center.
In a small bowl, mix together ½ cup softened butter, 1 tablespoon minced garlic, 1 tablespoon salt, and 1 tablespoon pepper.
Remove the neck and giblets from the 12–24 lb turkey and tuck the wings underneath.
Rub the butter mixture evenly over the entire turkey.
Place 1 tablespoon flour into the oven bag and shake to coat the inside.
Add 1 white onion (cut into chunks), 2 carrots (chopped), and 3 celery ribs (cut into pieces) into the oven bag. Place the turkey on top of the vegetables inside the bag.
Seal the oven bag with the included tie and place it in a roasting pan. Cut small slits in the top of the bag to allow steam to escape.
Bake according to the turkey size, until the internal temperature reaches 165°F:12–15 lb turkey: 2 to 2½ hours15–20 lb turkey: 2½ to 3 hours20–24 lb turkey: 3 to 3½ hours
Remove from the oven and let the turkey rest for 20 minutes.
Carefully cut open the oven bag, transfer the turkey to a serving platter, carve, and serve.
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Notes
Expert Tips
You can use a turkey breast instead of a whole turkey. Just adjust the cooking time.
To thaw a turkey properly, allow 24 hours for every 5 pounds of turkey to thaw in a refrigerator.
Make sure to cut 1 inch slits in the oven bag so the steam can escape.
When coating the turkey with the butter mixture, get all around. Don't miss any spots because this gives the turkey amazing flavor.