You have to be a Cosco member - when you go to the Cosco web site to request a referal, you have to enter your Costco number, and then theoretically, show your Costco card to the dealer to get a quote. They asked to see my card at Vista Lexus (Woodland Hills, CA), but I also got a qote on a BMW 325, and that dealer (Center BMW) gave me a quote over the phone without asking for any information, so I wouldn't be surprised if dealers vary in how they deal with this. You do have to have a Costco number to get the initial referal. Vista Lexus had a form with standard discounts - larger for the 250, smaller for the 350, but I got the larger discount for the 350 I bought. The whole thing was very easy - possibly becasue I had done a lot of research, and said that I was considering the 325i. I dealt with the fleet manager for the quote, but the sale was handled by a regular sales associate (Paige Grant - very nice and efficient). Considering that Thousand Oaks Lexus had quoted me a much higher price just a couple of months earlier, this was a pleasant surprise. They had to trade with another dealer to get me the car I wanted. Given the savings, it might be worth it to buy a Costco membership just to get the quote.
David