After a promising start from the away side, who were expected to get something from the game, Osawe took control to leave Gertjan Verbeek's side with nothing, Bochum's first defeat away to Kaiserslautern since 1998.
End-to-end start edged by Bochum
The hosts looked to make a quick start and won a corner within a minute of kick-off, the set-piece played short and out to left-back Naser Aliji, who curled just over. However, Bochum were looking for an early goal themselves, and should have got it when a flick sent Peniel Mlapa clear, but his shot was straight at the goalkeeper.
Bochum had the ball in the net within six minutes, however they weren't ahead as the assistant's flag prevented Felix Bastians from opening the scoring, having cleverly flicked the ball in from an outswinging set-piece. It was a tight decision, but the right one.
From then on, the away side were really in control and saw a glorious chance go begging when Thomas Eisfeld burst beyond his marker, squaring for Johannes Wurtz who opened his body up a little too much, diverting the ball wide.
Osawe's opener swings momentum
However, the opening goal came against the run of play, Kasierslautern taking the lead through Osawe just after the half hour mark. Taking advantage of Pavel Dawidowicz's slip, the forward drove into the area and let Manuel Riemann disappointingly beaten at his near post.
Bochum, having dominated the first half an hour, were shaken by the goal and wouldn't recover during the remainder of the first half, with Osawe focrcing Riemann into a good save to prevent the lead being doubled.
Two more in the second half for match-winner Osawe
Into the second half and Riemann couldn't keep Osawe out once more, with the forward doubling Kaiserslautern's lead less than 15 minutes into the second half. It came from largely nothing, Marcel Gaus finding an unmarked Osawe in the area with a dinked cross, Riemann powerless as he headed the ball into the back of the net.
Looking to finally wake up after going behind, Bochum did have a penalty shout not long after the second goal, as Eisfeld was bundled over in the box by an already-booked Philipp Mwene, however there was nothing doing according to the referee. Substitutions followed, with Dominik Wydra and Arvydas Novikovas entering the fray.
Those changes didn't seem to mame much impact, with the visitors only creating half-chances, such as an Eisfeld shot across goal evading Mlapa by a few inches.
Whilst it wasn't Mlapa's night, it certainly was Osawe's, and he sealed his hat-trick with 15 minutes remaining. Again finding himself in-behind the Bochum defence, Osawe was calm under pressure as he raced away to slot a calm finish past Riemann.
That proved to be the last significant action of the game, with Kasierslautern moving out of the relegation zone, scoring three goals in a game after having only managed four in their first nine games of the season. Bochum, meanwhile, remain 11th after a crushing defeat that does their promotion hopes no good at all.