Three first-half goals in the space of 10 minutes sentenced the O's to a fourth successive defeat as Crawley tasted victory for the first time in seven matches.
Orient edged the opening exchanges but lost defender Tom Parkes through injury before Steven Alzate was denied on the edge of the area by keeper Glenn Morris.
Crawley had failed to score in their previous three home games but leading marksman James Collins swooped to give them the lead with his 20th goal of the season midway through the half.
The former Shrewsbury striker struck by heading in a free-kick from Josh Payne and, although keeper Sam Sargeant got a hand to the ball, it flew into the corner of the net.
Crawley took a firm grip of the game by scoring twice in the space of four minutes before the interval.
Defender Joe McNerney rose unchallenged to head home a Payne free-kick from 12 yards on 29 minutes and then, from an Andre Blackman set-piece, Dutch midfielder Enzio Boldewijn forced the ball home.
Crawley, who had won only two of their previous 13 games, threatened again when a header from skipper Jimmy Smith was saved by Sargeant shortly after the break.
Boldewijn, after earlier firing wide from 25 yards, should have increased the lead when putting the ball wastefully wide from a pass by Collins.
Match support supplied by the Press Association.
Match ends, Crawley Town 3, Leyton Orient 0.
Second Half ends, Crawley Town 3, Leyton Orient 0.
James Collins (Crawley Town) wins a free kick on the right wing.
Foul by Sandro Semedo (Leyton Orient).
Delay over. They are ready to continue.
Delay in match Rhys Murphy (Crawley Town) because of an injury.
Corner,  Leyton Orient. Conceded by Lewis Young.
Foul by Rhys Murphy (Crawley Town).
Liam Kelly (Leyton Orient) wins a free kick in the attacking half.
Foul by Billy Clifford (Crawley Town).
Sandro Semedo (Leyton Orient) wins a free kick in the defensive half.
Billy Clifford (Crawley Town) is shown the yellow card.
Foul by Rhys Murphy (Crawley Town).
Callum Kennedy (Leyton Orient) wins a free kick in the defensive half.
Substitution, Leyton Orient. Henry Ochieng replaces Nigel Atangana.
Substitution, Crawley Town. Dean Cox replaces Enzio Boldewijn.
Attempt missed. Enzio Boldewijn (Crawley Town) right footed shot from the centre of the box is just a bit too high.
Attempt missed. Enzio Boldewijn (Crawley Town) right footed shot from the centre of the box is just a bit too high.
Attempt blocked. James Collins (Crawley Town) left footed shot from outside the box is blocked.
Attempt missed. Josh Payne (Crawley Town) right footed shot from outside the box is close, but misses to the right.
Delay over. They are ready to continue.
Substitution, Crawley Town. Josh Lelan replaces Andre Blackman because of an injury.
Delay in match Andre Blackman (Crawley Town) because of an injury.
Attempt missed. Rhys Murphy (Crawley Town) left footed shot from outside the box is close, but misses to the left.
Attempt missed. Gavin Massey (Leyton Orient) right footed shot from outside the box is high and wide to the right.
Corner,  Leyton Orient. Conceded by Joe McNerney.
Foul by Josh Payne (Crawley Town).
Liam Kelly (Leyton Orient) wins a free kick on the left wing.
Corner,  Leyton Orient. Conceded by Lewis Young.
Substitution, Leyton Orient. Rowan Liburd replaces Josh Koroma.
Corner,  Crawley Town. Conceded by Nicky Hunt.
Substitution, Crawley Town. Billy Clifford replaces Kaby because of an injury.
Corner,  Crawley Town. Conceded by Myles Judd.
Attempt saved. Jimmy Smith (Crawley Town) left footed shot from the right side of the box is saved in the bottom left corner.
Hand ball by Sandro Semedo (Leyton Orient).
Foul by James Collins (Crawley Town).
Sandro Semedo (Leyton Orient) wins a free kick in the attacking half.
Second Half begins Crawley Town 3, Leyton Orient 0.
First Half ends, Crawley Town 3, Leyton Orient 0.
Corner,  Leyton Orient. Conceded by Josh Yorwerth.
Leyton Orient's fading hopes of avoiding relegation from League Two took another heavy blow with a convincing defeat at Crawley.