In many Westerns the protagonist finds himself in a situation that calls for a decision to either stay home or fight. In Outland, Marshall O'niel's wife leaves him to travel to Earth. She is not leaving him because her love for him is gone, but rather because she can not deal with anymore wasted time spent in Space. Thus she prompts Marshall to travel to Earth with her and their son. Marshall decides to stay on the space station because he is filled with a sense of duty to follow through with him personal mission to fight for justice. This is similar to Martin in The Searchers when he consistently denies Laurie due to his need to complete the quest of finding and returning Debbie to where she belongs.
In The Outlaw Josey Wales, Josey Wales utilizes the "wild west" environment to his advantage. For instance, when the antagonists are crossing the river by boat (which is on a rope levy, Josey Wales shoots the rope, causing the antagonists to be stuck. Similar to this, Marshall utilizes his environment to his advantage. Some examples include: he strategically plants his guns into hidden areas of the station for later usage, and he lures the bad guys into certain locations of the station where he can use the forces of space to kill them.
In addition to fully utilizing one's environment, an important aspect of Westerns is the feeling of isolation from town to town. In Outland the space station serves a similar purpose. It is isolated and later on becomes a trap for Marshall. He is unable to leave. On top of everything a time countdown for when the on coming ship is arriving helps to build tension. Everyone on the ship knows that they people arriving are coming to kill Marshall. But even with this information Marshall can not leave.
When Marshall presents the doctor with the blood samples, at first she is skeptical that they will discover anything. But because this is a sci-fi, the technology is smart enough to detect the drugs in the blood. The whole concept of hiding the drugs in this massive corrupted scheme is similar to the corruption of bad guys in a Western.
Adding to the tension, Marshall is not only on an isolated ship, but when the people assigned to assassinate him arrive, everyone congregates in the bar, leaving Marshall all alone (except for his one trusted friend, the Doctor) with the assassins.
Outland definitely effectively utilizes both stylistic aspects of sci-fi and western to create an intense, action-packed film.