How long should i cook 5 big peices of thawed chicken ?

That depends on how you cook them and how large they are etc. Most average chicken s with bones and skin will take about 35 minutes to cook in a preheated 375 degree oven. You can always cut it open and if the juices are clear then they are done. Boneless skinless chicken will take less time - usually 20 to 30 minutes.