The first day of the competition, staged at Horse Guards Parade in the heart of London, saved the best until last with a clash involving three of the most successful women in the sport starting at 11pm.
May-Treanor and Walsh, who triumphed in Athens in 2004 and in Beijing four years later, are the only pair to have won two Olympic golds in beach volleyball and they opened with a two sets to love victory in Pool C.
Cook, who picked up bronze in Atlanta in 1996 and gold in Sydney in 2000 with former team mate Kerri Pottharst, is the first Australian woman in any sport to compete in five Olympics.
Despite the chilly night air, the pairs delivered a stunning display of powerful spiking, muscular blocking and dramatic diving that had the crowd on its feet.
The Americans won 21-18 21-19 in a contest that was hard-fought until the last second. The match point was a thrilling rally that had spectators gasping and cheering multiple times until it finally went the way of May-Treanor and Walsh.
"Any time you face Nat Cook you're in for a battle ... They're a great team. They pushed us to our limit," May-Treanor, 34, said.
Since the win in Beijing, May-Treanor injured her Achilles tendon rehearsing for the hit TV show 'Dancing With The Stars' while Walsh, 33, had two children less than a year apart.
Both players said they felt strong despite having taken time away from the game and Walsh said being a mother was a plus.
"It's more special. I'm playing with a fuller heart, and my heart was full before, and I'm playing with more inspiration.
I'm just more grounded. I think when you're grounded in your life you perform better," she said.
The game is played barefoot in the sand and women normally play in bikinis but both the Americans and the Australians covered up somewhat given the late hour.
Bikinis being a hot topic for media covering the sport, both teams were asked multiple questions about their choice of clothing.
"It's cold. It's 11pm in London," was Walsh's laconic response.
Hinchley and Cook wore black leggings and tight white tops under green sports bikini tops. May-Treanor and Walsh sported red bikini bottoms with skin-tight long-sleeved black tops.
Cook looked like she was loving every minute of her fifth Olympics, smiling, laughing, pumping her fists and blowing kisses to big cheers from an enthusiastic crowd in the 15,000-seater stadium.
"I love the energy of the crowd. I really work the crowd for the energy," said Cook, 37.
"I know this is my last Games so I'm going to enjoy every single moment I can. In our last match, hopefully it's the gold medal match, but someone will have to drag me off the sand kicking and screaming."
Built on Horse Guards Parade, a vast esplanade next door to Prime Minister David Cameron's residence at 10 Downing Street, the stadium affords spectators stunning views of the Big Ben clocktower and the London Eye, a giant Ferris wheel.
Beach volleyball is popular in Australia and in the US states of California and Florida and the two countries are among just three to have won Olympic gold since the sport made its Games debut in Atlanta in 1996. The third is Brazil.
The rivalry between the two powerhouse nations created an electric atmosphere and crowds were pumped up with blaring pop music in between points and digital screens that displayed comments such as "AMAZING", "FIRED UP!" and "BOOM!" after good rallies.
On a good night for the US, May-Treanor and Walsh were preceded on court by compatriots Jake Gibb and Sean Rosenthal who beat first-time Olympians Grant Goldschmit and Freedom Chiya of South Africa 21-10 21-11 in Pool D.
Gibb and Rosenthal, who came fifth in Beijing, look like strong contenders for a medal after a remarkable run of form since changing coach earlier this year.
The surprise of the day came in the first match when lowly-ranked Russian women's pair Anastasia Vasina and Anna Vozakova upset Beijing bronze medallists and London medal favourites Zhang Xi and Xue Chen of China 18-21 21-14 16-14.
However, the Chinese still have a chance to make the podium as the competition is in a pool stage and will progress to a knockout phase later.