EXCLUSIVE

"Real Housewives of Beverly Hills" producers have lured back 2 big stars ... one of whom they fired.

Camille Grammer and Adrienne Maloof are the secret to restoring the show to its former ratings glory ... at least that's what producers are banking on -- sources connected with the show tell TMZ.

Pretty ironic ... Camille was fired after her divorce from Kelsey. Her problem ... she went from crazy to boring after her divorce.

Adrienne was a hell-freezes-over type girl, because we're told producers said they would NEVER work with her again after she quit the show.

But times and ratings change. Now that the show has 86'd Carlton Gebbia and Joyce Giraud crashed and burned, there was a gigantic hole in the cast ... now filled.

We're told Camille and Adrienne won't be on all the time ... they'll be on here and there. They've already shot scenes -- most recently at Kyle Richards' infamous white party.