Question: how long does it take to cook a chicken at 275?
Answer: Remove the pack of giblets from the chicken. Save for use in homemade stock, if desired. Place the chicken in a roasting pan. ... 
Bake, uncovered, at 275 degrees F for 3-4 hours. If chicken is smaller, cook on the low end of the time frame and vice-versa. ... 
Let the chicken rest for 10-15 minutes before carving.