You can take advantage of the deal by uttering the words "Outback Bowl" to your server.
The Bloomin' Onion is one of Outbacks signature dishes and is basically an onion that is cut so that it will 'bloom' while frying that is then is battered and deep-fried and served with spicy bloom sauce. It's typically $6.99 for an order (may vary).
The offer is only good for dining in at participating Outback restaurants.