Looks like actress Mischa Barton should have bought in The OC instead of Beverly Hills, as she is now $100K behind on her mortgage payment on her $6.4 million home, according to TMZ.

Barton just got slapped with a default notice — obtained by TMZ — informing her she’s skipped more than 100 grand in payments … triggering the foreclosure process.

The crib is awesome — 8 bedrooms, 11 baths, 3 guesthouses all on 1.2 acres. She bought it for $6.4M in 2005 — when “The O.C.” was a big deal, and took out a loan for $4.2 million.

The show went off the air in 2007 — and Mischa’s been trying to unload the house since 2010 … when she listed it for 8.695M, but no one bought it. She re-listed in 2011, and again … no takers.

Her last ditch effort was attempting to lease it for $35K/month last year … but that move appears to be way too little too late.