when I drive my car the anti freeze goes back into the resivior and drains the radiator and pours on the ground

It drains all the coolant or is it merely overflowing a bit when hot? Check all your radiator hoses for leaks as well as the radiator. I don't think it is possible for all the coolant to drain out via the overflow tank. If you have a bad head gasket it may be that hot gases from the engine are blowing all the coolant out the radiator.

ricsie- just to let you know, Subaru recommends their own "super coolant " which is designed to last longer than other brands on the market.

so whats leaking....????

I agree, likely a blown head gasket is pressuring up the system and causing the coolant to be forced out.

Test the cap first. Many head gaskets have been done on these cars b/o a weak cap.

Don't know how many miles are on your car, but, if you drive an average 12,000 to 15,000 miles per year , you would be around 135,000 to 150,000 miles now. It's not unheard of to have head gasket issues at this mileage, and the mid 2000s Subaru cars had this problem. Fortunately, you can get a new multi layered head gasket as a replacement which will greatly reduce the chance of this happening again. The multi layered head gaskets have proven to be much more durable introduced on the 2010 models forward. I would definitely recommend talking to your mechanic about the new design and make sure that you get the upgrade, especially if you intend to keep your car. Do a web search to learn about the multi layered head gaskets, there's plenty of information about them out there. Good luck.

Unlike the great majority of atmospheric-pressure (gravity) head gasket leakage...which can be nursed along by adding coolant periodically...you have the rarer COMBUSTION-pressure leakage into the coolant system; the resultant pressurization of the coolant system quickly overwhelms it and blows hot combustion gases through the radiator and percolates out the expansion tank. Only repair is a $1500-1800 (off-dealer) HG replacement. Don't bother stuffing conditionerrs nor glues into the cooling system, as you may just end up gumming up the radiator or heater core too. Sorry about the bad news. Oh! There's a very small chance that your rear heater hoses and/or the radiator are blocked with contamination (or the latter occluded by mud/sand/leaves), but unlikely. You can back-flush the heater hoses easily to check. Also note that a non-OEM (smaller bore) thermostat WILL cause overheating at high speed or hill-climbing. So check this simple stuff before committing to a HG job. Good luck.

I agree with the "TheSubaruGuruBoston", excellent advice and explanation. If you're planning on keeping your car and everything else is working fine, then get it done correctly. Still would advise you to throughly check out the multi layered head gaskets. Once this is done, along with the timing belt issue, you're good to go for another 100,000 miles. And, a 2005 car is still relatively young for an Outback. There's a lot of these cars going to 250,000 miles and more. Just check out the Subaru high mileage club. Finally, it's always less expensive to repair your existing car vs. a new replacement vehicle with 60 months of car payments, higher insurance premiums etc. Find a good independent mechanic who specializes in Subaru cars or better yet somehow referred to you. Good luck.