Roasting a free-range v. a standard supermarket chicken

[Mobile Chicane]

Whenever I roast a standard 1.5Kg supermarket chicken, it gets a 20 minute 'sizzle' at 220C to crisp the skin, then 50 minutes at 180C to cook through. Just seasoning, no oil or butter on the skin. Always perfect.

Try the same method on a denser, free-range bird of the same weight and it's a tad dry. What am I doing wrong?

Should I cover with foil? Lower the initial heat? Rub with butter? Shove an onion in the cavity? All of the above?

[Mobile Chicane]

Thanks - I'll try the brining.

What concentration are you using, and does the skin still crisp?

I'm presuming you pat it dry with kitchen towels etc before cooking.