@PiecesofMargo Obviously having a thermometer helps. Or if you have good kitchen shears and knife, you can spatchcock the chicken to make it cook faster and more evenly.
@PiecesofMargo The surest way, if you can wait is to cook at like 275 or 280 for maybe 45 minutes. Check doneness if meat and then crank the oven up to 400 for maybe 5 minutes. Other way is to start high at 400 and then bring oven temp down to 350 (or lower) for maybe 25 minutes.