Yes, QUARTERED is a Scrabble word!

Letter values in Scrabble US: Q 10, U 1, A 1, R 1, T 1, E 1, R 1, E 1, D 2.

Is it a valid word?

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

provide housing for (military personnel)
pull (a person) apart with four horses tied to his extremities, so as to execute him
divide into quarters
divide by four; divide into quarters

Also: draw and quarter.