New Forest boss Billy Davies this week called on his two midfielders to chip in with more goals after both broke their ducks in Tuesday's 6-1 drubbing of Huddersfield.
And they were clearly paying attention as Polish midfielder Majewski, who had not found the net in his first 20 games, made it four in two matches while Lansbury doubled his tally for the campaign.
Hosts Charlton were never in the game even before they were reduced to 10 men late in the first half when Yann Kermorgant saw red.
Forest were dominating and their best chance of the opening half fell to midweek hat-trick hero Majewski, but he made a mess of his 22nd-minute effort.
Majewski also toe-poked straight at Addicks goalkeeper Ben Hamer while Chris Cohen and former Valley skipper Andy Reid blazed shots over.
Charlton were already up against it but Kermorgant did them no favours by getting himself sent off for clashing with Greg Halford in the 37th minute.
The French striker aimed a kick at Forest defender Halford off the ball and, after consulting with his assistant, referee Andrew Madley showed him a straight red card.
Charlton made it to the break all-square but lasted just eight minutes of the second half before Majewski struck.
Reid found the Pole in the area and, although his touch appeared heavy, it took him past a couple of defenders before he prodded the ball past Hamer.
Lansbury then had a shot deflected narrowly wide, but the former Arsenal midfielder's luck was in on the hour mark.
Hamer badly fumbled a weak shot from Simon Cox and Lansbury was gifted a tap-in from inside the six-yard box.
It was almost 3-0 moments later but Hamer managed to scramble Elliott Ward's flick against a post, before Majewski wasted another good chance when he blasted over the top again.