The Doonhamers suffered a major blow to their play-off hopes when they went down to a heavy defeat at Kirkcaldy.
Queen's Millar had gone close before Stewart's 23rd-minute opener when he fired into the top corner.
Ian McShane had two near things for the visitors before Stewart netted with another strike on 78 minutes.
Lewis Vaughan then wrapped up the win when he found the bottom corner from 14 yards, leaving fourth-placed Queens just one point ahead of Falkirk.
Lineup, Bookings (4) & Substitutions (6)
Raith Rovers
- 20 McGurn
- 02 Thomson Booked
- 55 Barr
- 04 Watson
- 23 McKeown
- 07 Anderson (McKay - 83' )
- 06 Fox
- 12 Callachan (Scott - 65' )
- 14 Conroy
- 09 Stewart
- 16 Vaughan (Elliot - 87' )
Substitutes
- 01 Cuthbert
- 05 Hill
- 10 Elliot
- 11 Scott
- 19 McKay
- 30 Robertson
- 31 Matthews
Queen of the South
- 01 Clark
- 04 Dowie
- 05 Durnan Booked (Reilly - 56' )
- 06 Higgins
- 03 Holt Booked
- 12 Kidd (Mitchell - 71' )
- 18 McShane (McKenna - 85' )
- 08 Millar
- 17 Carmichael
- 15 Paton Booked
- 19 Lyle
Substitutes
- 02 Mitchell
- 10 Reilly
- 14 McKenna
- 20 Atkinson
- 23 Smith
- 24 Smith
- 28 Pickard
Ref: Craig Charleston
Att: 1,152
Images courtesy of Colin Johnstone and his team at Kirkcaldy