Yes, OVERAGE is a Scrabble word!

Letter values in Scrabble US: O 1, V 4, E 1, R 1, A 1, G 2, E 1.

Is it a valid word?

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

a surplus or excess of money or merchandise that is actually on hand and that exceeds expectations

Also: over-the-hill.