They succeed Jeff Binder and Rebecca Luker, who played their final performances Feb 27.
Kenzler and Osterhaus are reprising the roles they originated in the North American touring production of Poppins.
Kenzler has also appeared on Broadway in Twelve Angry Men, The Caretaker and Dinner at Eight and Off-Broadway in The Tempest, Hamlet, Spinning Into Butter, The Charity That Began at Home and his one-man show, Fire In The Head.
Osterhaus rejoins the Broadway cast, having understudied the roles of Mary and Winifred Banks. She made her Broadway debut as the understudy for Sophie in Mamma Mia!
The Broadway cast is currently headed by Laura Michelle Kelly in the title role with Christian Borle as Bert.
Produced by Thomas Schumacher of Disney Theatrical Productions and Cameron Mackintosh, Mary Poppins celebrated its three-year anniversary at the New Amsterdam Theatre on West 42nd Street on Nov. 16, 2009.
Richard Eyre directs Mary Poppins, which features choreography and co-direction by Matthew Bourne and boasts original songs from the film — with music and lyrics by Richard M. Sherman and Robert B. Sherman — as well as new songs and additional music and lyrics by George Stiles and Anthony Drewe. Julian Fellowes wrote the book.
The musical also features set and costume design by Bob Crowley, co-choreography by Stephen Mear, lighting design by Howard Harrison, sound design Steve Canyon Kennedy, orchestrations by William David Brohn, musical direction by Brad Haak and musical supervision by David Caddick.
For more information visit www.DisneyonBroadway.com.