Forest, who sacked Billy Davies on Monday, were booed off the pitch by the disgruntled home faithful after a lifeless and abject performance which would have given any potential managerial candidate plenty of food for thought.
Resolute Charlton were full value for the three points, with an accomplished showing that constantly frustrated Forest and they could have won by a bigger margin as they also hit the woodwork through Marvin Sordell.
With Neil Warnock rejecting the chance to replace Davies in the Reds’ hotseat, academy manager Gary Brazil was handed the task of restoring lost pride following their hammering at bitter rivals Derby at the weekend.
Brazil brought Darius Henderson, Greg Halford and Djamal Abdoun back in to the Reds’ starting line-up, while Danny Fox continued at left-back after Lee Peltier’s loan move from Leeds collapsed.
Charlton also made three changes with Reza Ghoochannejhad, Sordell and Astrit Ajdarevic coming into the starting XI as Addicks boss Jose Riga looked for a response to their 3-0 defeat by Burnley.
Forest created an early chance when Abdoun and Fox combined down the left flank, with Fox delivering the perfect cross for Jamie Mackie, who headed narrowly wide.
Gonzalo Jara created some space for himself in midfield and slotted a lovely ball through for Henderson, whose first-time effort fizzed just past Ben Hamer’s left-hand upright.
The hosts, though, nearly fell behind after 20 minutes. Cousins latched on to a ball over the top that left the home defence flat-footed and he slipped a pass across the area for Sordell to run on to, but his effort crashed off the foot of Karl Darlow’s left-hand post and away to safety.
After 25 minutes of mediocrity from both sides, Simon Cox almost snatched a Forest opener in first-half stoppage-time, but his shot from Abdoun’s pass rebounded off a post and in the ensuing melee, Henderson’s header was acrobatically saved by Hamer.
Richard Wood replaced fellow centre-back Dorian Dervite at the break for Charlton, while six minutes into the second half, Forest brought on Jamie Paterson for Cox.
The visitors were comfortably keeping Forest at bay and as the home fans’ groans grew louder, Charlton sensed this could be their opportunity to get something from the game, with Diego Poyet, Ajdarevic, Cousins and Ghoochannejhad growing in stature for Riga’s side in the centre of the park.
The unmarked Cousins then fluffed his lines, though, as he cracked Lawrie Wilson’s cross over Darlow’s bar, while down the other end, Henderson summed up Forest’s night far by wildly blazing a shot wide and he was instantly replaced by Rafik Djebbour.
Fox curled a 70th-minute free-kick just off target after Paterson had been fouled on the edge of the area, Djebbour nodded Paterson’s cross inches over the bar and then Charlton keeper Hamer kept out Halford’s bullet header as Forest finally created some chances.
Charlton, though, delivered a fatal shot across Forest’s boughs 10 minutes from time as Cousins slotted into an empty net from 12 yards after sub Jonathan Obika’s shot had crashed off a post straight into his path as the home defenders just stood and watched.
Paterson cracked a free-kick over the bar and Danny Collins headed over in injury-time as Forest’s chances of rescuing a point evaporated.