Much was expected of Gary Megson's team who had four straight league wins behind them but after conceding a sixth minute goal to a 30-yard thunderbolt from Phil Jevons they seldom looked like salvaging the match.
Jevons again went close in the 14th minute, bringing a great save from Russell Hoult with a free-kick, but he was in unstoppable form and in the 24th minute he made it 2-0.
Referee Jarnail Singh allowed advantage when Matt Harrold was fouled and a clever move down the right ended with a pass from Kevin Amankwaah which Jevons knocked in.
By this time both sides had lost key players. Forest winger Kris Commons limped off in the 16th minute following a tackle and almost immediately the Glovers lost their inspirational centre-half Terry Skiverton who was ill.
Skiverton was replaced by Scott Guyett - back from a loan spell with Aldershot - and he came close to scoring a third right on half time when he met a Colin Miles cross with a perfect header that thumped against a post.
Six minutes earlier Forest had been reduced to 10 men when Gareth Taylor was straight red carded following an off-the-ball incident with Miles.
The second half saw Yeovil again applying the pressure and new manager Steve Thompson, who has been demanding more goals, should have seen the scoreline double.
Crosses from both wings eluded striker Pablo Bastianini, although the Argentinean had his best game yet.
Eventually it was left to midfielder Arron Davies to add number three with eight minutes remaining.
Substitute Kevin Gall slipped a neat pass from the left to the edge of the box and this time keeper Hoult, who had done everything that could be expected of him, had no chance as the ball whistled in off the underside of the bar.