The West End star will play the Lady of the Lake in a touring production of the Monty Python Tony Award-winning show.
"I've been very lucky to play such a fabulous part as Nancy in Oliver!, and now also to play the fabulous diva called Lady of the Lake - I'm over the Monty moon," said Prenger.
"I love Spamalot so it's a great opportunity to take part in such a fun show. I can't wait."
The UK tour kicks off on May 29 at London's New Wimbledon Theatre.
Yesterday, it was revealed that Prenger would be leading the hunt for a Toto as part of Andrew Lloyd Webber's new reality series Over The Rainbow.