Atlanta made its debut Sunday following Minnesota United's bow Friday as the league expands from 20 to 22 teams this season.
But the Red Bulls spoiled the party thanks to late goals in front of 55,297 fans at Bobby Dodd Stadium in Atlanta.
A cross from Tyrone Mears found its way to Yamil Asad at the back post and the Argentine midfielder — on loan from Velez Sarsfield — made no mistake from inside the 6-yard box to celebrate Atlanta's first MLS goal.
Atlanta's lead should have been more, and the Red Bulls capitalized in the second half thanks to Daniel Royer in the 76th minute. Tottenham loanee Anton Walkes then turned the ball into his own net six minutes later as the visitors from New York silenced the hosts.
It was also a landmark night as Orlando opened its new stadium with a 1-0 win over New York City FC.
Cyle Larin ensured Orlando's stadium opener resulted in maximum points, despite an injury to captain Kaka in the first half.
Kaka was forced from the field with a hamstring strain in the 11th minute, but Larin's close-range header four minutes later downed David Villa and Andrea Pirlo in front of a capacity crowd.