Adler reportedly first popped the question during a vacation in Italy last year.
The actor revealed about his engagement at the 'Emmys: 12th annual Heller Awards' event in Beverly Hills, reported Us magazine.
"She was getting ready for an hour or so, so I went outside to take a stroll to some ring shops," Adler said.
"Max was sneaking off and picking rings unbeknownst to me to surprise me. The ring is from Rome," Bronstein added.
The couple, however, are not planning to get married anytime soon.
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Adler and Bronstein plan to invite all of "Glee" castmates to their wedding.
"Everybody. I want them to sing. I already committed Darren Criss to giving a song," Addler said.
Adler was on "Glee" from 2009 to 2012.