Yes, COOKIE is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, O 1, K 5, I 1, E 1.

Is it a valid word?

COOKIE is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any of various small flat sweet cakes (`biscuit' is the British term)
the cook on a ranch or at a camp
a short line of text that a web site puts on your computer's hard drive when you access the web site