Forest were 2-up inside the first half-hour with strikes from Felix Bastians and Scott Dobie after 20 and 24 mins respectively.
Howson pulled a goal back before the break on 38 mins with a stunning 25-yard free kick but Kevin James scored Forest's third 12 minutes into the 2nd half to more-or-less put them in control and make the points safe.
Lewis McGugan made it four a minute from time.
Leeds: Lund, Madden, Camfield (Grace 80), Wilkinson, Hird, Bayly, Ameobi (Cartman 74), Gardner, Beckford, Howson (Brown 63), Rose.
Subs Unused: Edwards, Stansfield, Hotchkiss.