The Teen Titans made their first appearance as a team in Brave and the Bold #60 (June-July, 1965), fighting the Separated Man (which also featured the premiere of Wonder Girl)....but, the teens gathered together a few times before that as well!
The Secret Olympic Heroes
This involved some superior archery by Speedy, and the help of one of the young athletes, Davey Bradley, who ran a special race to save the team and look good in front of his father, Ted Bradley.
...so, looking forward to go back....
In The Beginning...
...after the Crisis, it appears the fab four Teen Titans were guests at the wedding as well, as related in Brave and the Bold #10 of April, 2008.
The Thousand-and-One Dooms Of Mr. Twister
Robin, Kid Flash and Aqualad) did meet one time before in Brave and the Bold #54 (June-July, 1964 by Bob Haney, Bruno Premiani and Sheldon Moldoff), when they faced Mr. Twister in the town of Hatton Corners. Mr. Twister kidnapped the youths of the town, and used the power of his magical Indian medicine staff to control the weather, which was enough to even take Kid Flash and Aqualad out of the way. Luckily, Robin was there to put an end to the trouble caused by Brom Stikk (the man who called himself Mr. Twister...
....who would later come back to menace Robin and the Teen Titans under another identity, and even later with more help as well!).
Wonder Girl), then in Showcase #59 (November-December, 1965), leading to Teen Titans #1 (January-February, 1966)....and from there into history, adding members like Hawk & Dove, Lilith, Mal, Gnarrk, Joker's Daughter, Golden Eagle and more!