After small beginnings three decades ago with just a few friends at one of the legendary beer tents, "Pink Wiesn" as it is known, has become a tradition at Munich's annual event, and a fixture on the global gay party calendar.
Soon after the opening Sunday morning, Los Angeles native Rozeboom, 30, toasted his wedding engagement just two days before with his fiance, Trent Dempsey, and two big glasses of German beer.
"I just love the fusion of the traditional with gay culture -- it's a wonderful feeling," Rozeboom, a bar manager, said.
"We didn't want to miss this while we were in Europe, especially after we got engaged," added Dempsey, also sporting lederhosen hastily bought from a vendor at the main railway station.
Gay Oktoberfest is held each year on the Sunday of the opening weekend at the Wiesn fairgrounds' Braeurosl tent, named after the fabled beauty Rosi, a daughter of the Pschorr beer dynasty.
It started with a misunderstanding, when Munich Lions' Club, a local gay fetish group, reserved a few tables at the tent and organisers mistook the name for a football team.
But as the numbers grew each year, the Heide family, who have run the tent since 1936, turned over more and more of its 6,200 capacity seating to gay party-goers until the semi-official "Pink Wiesn" was finally established.
Revellers began lining up at dawn to grab a table inside and by the opening at 9:00 am (0700 GMT), the tent was full to the rafters.
The beer chugging, table dancing, thigh slapping, drinking song antics of the more traditional tents can all be found at Rosa Wiesn, and nearly everyone wears Bavaria's festive "Tracht" clothing.
But along with oompah music, the soundtrack is leavened with Lady Gaga, Kylie Minogue and Madonna dance tracks.
- Culture war battleground -
While politics is customarily left outside the beer tent, the talk this year frequently turned to Germany's "backward" ban on gay marriage following major strides made by proponents in Ireland and the United States.
Germany introduced civil unions for gay and lesbian couples in 2001, but they still do not have the right to marry and are forbidden from adopting children together.
"America is the prudest country the world has ever seen and even they are ahead of us on gay marriage," said 58-year-old travel agent Wolfgang Lies, nursing a wheat beer with two friends.
The CSU, the Bavarian sister party of Chancellor Angela Merkel's conservatives, is seen as the fiercest opponent of extending full marriage rights, making the predominantly Catholic heartland a key battleground in the culture wars.
Lies has been coming to Gay Sunday at Oktoberfest since the 1980s and remembers well when gay couples had to be discreet or risk bashing by drunken visitors of the beer fiesta when they left the tent.
"We're just like everyone else and now expect to be treated like it," he said.
James Ratledge of the Munich Bears, a gay group of stout, hairy-chested men recalling their mascot, said greater diversity had also helped Oktoberfest, an event dating back to 1810 that now draws six million people a year.
"The Bavarians are very proud of their traditions and that means us gay Bavarians too," he said.
"No one from here would think of going to Oktoberfest without their Tracht because even ugly people look good in it," he said with a laugh. "It's flattering to the figure."
Ratledge said that despite the hot, sticky atmosphere that can develop in the tent, the organisers enforce a strict shirts-on policy.
"Once one person takes his off, they all will. We want to keep it decent," he said.
Susanne Hoffmann, a 48-year-old waitress at the tent operated by Hacker-Pschorr, one of Munich's six brewing giants, heaves eight glass litre mugs to a table of bearded men with a smile.
"Gay Sunday is the best day of Oktoberfest," she told AFP later. "There are no fistfights, everybody is nice and easy-going. And the music is better too."
With a grin, she quoted a famous local drag queen who performs each year at the event: "A bissl Leder braucht a jeder" (Everybody needs a little leather).