As others have hinted, this film is beyond most people's idea of merely quirky. In fact, it's slightly unbalanced and in parts borders on insane... yet somehow what emerges is a film that is just about believable, as are the various colourful characters who act it out. The film is great fun, and its two hours go by quickly.
Being a huge fan of Brando, and an admirer of Nicholson, I end up thinking this film in no way detracts from their illustrious careers and what they've done elsewhere. Having said that, Brando does ham it up in a grand, thoroughly camp style: outlandish costume, inexplicable changes of costume, florid gestures and - as other reviewers have pointed out - weird accents. The accents he uses shift around inconsistently and theatrically (especially the more sustained efforts to sound Irish in his early scenes). But he obviously had fun when making the film. Nicholson's performance is a model of seriousness and sobriety by comparison.
The cinematography is superb, with great use of light and shade in shooting a wonderful landscape. The action is generally slow-paced, but with a heavy sense of impending menace through most of the film. The score is not among the film's stronger points. Dialogue is mostly fresh and original for a 70s era western, and cliché avoided. It is well acted, despite the quirkiness of the script and screenplay.
Perhaps a little odd that the critics slated this film so ferociously at the time it was released. Butch Cassidy and the Sundance Kid, made just a few years earlier was (rightly) lauded to the skies, precisely for giving originality, humour and a modern twist to the old western format. That film now seems in some ways more dated than The Missouri Breaks. The latter is not as good a film as Sundance, by a distance, but, for any true fan of cinema, well worth giving it a try.
