The actress - who plays rich girl Sugar Motta in the Fox sitcom - will return as a recurring cast member for its fourth season, reports TVLine.
Lengies joined the Glee cast last year as the self-appointed lead singer of rival group The Troubletones, before joining up with New Directions.
Fox president Kevin Reilly said at the Television Critics' Association's summer press tour that Glee's new season will split its focus between McKinley High and NYADA, where Lea Michele's Rachel is attending her first term.
Chord Overstreet has also signed a deal that sees him boosted from recurring to a series regular as Sam Evans in the fourth season.
Matthew Morrison has hinted that the next season will feature a wedding between two characters.
The new season of Glee premieres with 'The New Rachel' on September 13 at 9pm EST on Fox in the US.