Liev Schreiber has signed on to costar in P.J. Hogan’s “Mental,” joining “Little Miss Sunshine” thesp Toni Collette.

Universal Pictures Australia will distribute the pic in Oz and New Zealand; pic does not yet have a U.S. distrib.

Jerry Zucker, Janet Zucker, Todd Fellman and Jocelyn Moorhouse will produce “Mental,” written and directed by Hogan.

Cast also includes Aussie thesps Anthony LaPaglia (“Without a Trace”) and Rebecca Gibney (“Packed to the Rafters”).

Pic centers around Shaz (Collette), a crazy hotheaded hitchhiker brought on to nanny five girls by their father, a philandering politician, after he hospitalizes his wife for a nervous breakdown.

“Mental” will reunite Hogan with Collette, who last collaborated on 1994’s “Muriel’s Wedding.” Pic will also mark Hogan’s first Australian shoot since “Wedding.”

“Like Muriel’s Wedding, ‘Mental’ is a comedy laced with pain and brimming with flawed but lovable characters,” Hogan said. “Shaz is hilarious, outrageous, dangerous, courageous, inspiring, heart-breaking and totally, totally mad.”

Story Bridge Films and Zucker Prods. will begin the three-month “Mental” shoot July 25.

Schreiber’s recent credits include “Salt” and “X-Men Origins: Wolverine.”

Hogan, who helmed the Julia Roberts-toplined “My Best Friend’s Wedding,” last directed 2009’s “Confessions of a Shopaholic.”

CAA reps Schreiber, Hogan, LaPaglia and Zucker Productions.