Bryson grabbed the opening two goals before Jeff Hendrick sent Derby into half-time 3-0 ahead.
Johnny Russell added a fourth before Bryson completed the rout, and his hat-trick, from the penalty spot on 69 minutes.
Derby's win kept their slim automatic promotion bid alive, while also dropping Forest out of the play-off places as they went an eighth games without victory.
Reading profited on Forest's latest slip with a 2-1 win at Birmingham enough to move them up to sixth.
Second-placed Burnley maintained a 10-point lead over Derby, in the race for automatic promotion, as they brushed aside relegation-threatened Charlton 3-0 at The Valley.
Ashley Barnes' first-half opener was followed by a Sam Vokes penalty and a late Michael Kightly strike.
Lewis McGugan had sent Watford ahead but Wigan, who saw their eight-game wining run ended in a 3-3 draw with Yeovil in midweek, bounded back to move five points clear inside the play-off places.
Yeovil missed the chance to climb out of the relegation places as they threw away a two-goal lead to draw 2-2 at home to Bolton, who ended the game with 10 men.
Ishmael Miller and Kevin Dawson sent the Glovers 2-0 up and while Lukas Jutkiewicz pulled one back Yeovil should have made the game safe when Alex Baptiste saw red.
Miller missed the ensuing penalty and was made to pay when Zat Knight headed in a looping equaliser moments later.
The Glovers' bottom-three rivals, Barnsley and Millwall, both lost.
Bournemouth defender Steve Cook's injury-tine strike goal condemned last-placed Barnsley to a 1-0 defeat while the Lions fell 2-1 at Leeds.
Matt Smith scored first before the Championship's top scorer Ross McCormack bagged his 26th goal of the campaign. DJ Campbell pulled a goal back for the Lions.
Doncaster moved eight points clear of danger with a 1-0 win over close rivals Sheffield Wednesday. Chris Brown scored the winner on 32 minutes.
Ricardo Fuller scored the only goal after four minutes as Blackpool beat Huddersfield 1-0 while Brighton lost 2-0 at home to Ipswich after second-half gaols from Tommy Smith and Daryl Murphy.
- Sports & Recreation
- Jeff Hendrick