I have a Subaru 2002 outback 70,000 miles on it?

There is something wrong with the car. I have a 1997 Outback wagon with 137,000 miles on it, and it burns no oil. If you've got a concrete drive you can park it on (or a large sheet of paper you can lay down), you'll soon find out if it's dripping oil while not running. If it's leaking only while running, you'll find fresh oil on the underside of the engine/transmission. Have you checked the coolant for signs of oil?

If none of the above explain the oil loss, check each spark plug for fouling from a leaking cylinder. You should be able to see blue smoke from the exhaust; however, if you're burning and not smoking, a simple emissions test will show it.

By "Subaru Garage" did you mean the Dealership? If not, take it to the actual Dealer. They know the cars best.

Added:

My Subies get Valvoline Durablend semi-synthetic oil and love it (Change them every 5,000 miles). I put only Mobil 1 in my Porsche.

My dad's jeep used to burn a small amount of oil but you really never saw any smoke except on cold starts and after towing our travel trailer.

Is there any oil drips on the ground of where the car is parked? Another possibility is that whoever is filling the oil isn't putting enough in so when you check the oil level after driving it for a while you think its being burned off.

My dad solved the slight oil burning problem by adding a bottle of Lucas Oil Engine Oil Stabilizer (round white bottle) after an oil change. No smoke after that!

If there is no obvious leak and no noticeable smoke, then it's no easier for people on line to try to diagnose than the shop you took it to. The only thing I can suggest is to try a different brand oil or even a slightly thicker weight. I know in my WRX, some brands burn at a much higher rate then others. I like castrol or penzoil for regular synthetic or Redline or Amsoil for a higher performance synthetic. Mobil and Havoline burn like crazy in my car and I will never use them or recommend them to anyone.