McClaren was looking for back-to-back wins for the first time since taking charge of Forest and could not have wished for a worse start as his side went 3-0 down inside the opening half-hour.
Jay Rodriguez capitalised on some poor Forest defending to head Burnley in front after five minutes and he made it 2-0 with another header in the 15th minute. Chris McCann virtually sealed Forest's fate with 29 minutes gone, prompting scores of visiting fans to head for the exits.
Ross Wallace made it 4-0 just before the break and Ishmael Miller got one back for Forest in the second half before Charlie Austin wrapped up Burnley's first home league win of the season with an excellent header.
Forest had conceded more first-half goals than any other team in the npower Championship going into the match and almost inevitably they conceded another with five minutes gone.
The frail Forest defence failed to deal with Brian Easton's cross from the left and Austin nodded the ball across goal for Rodriguez to head in from close range.
Forest were in disarray and Burnley doubled their lead 10 minutes later when Junior Stanislas was afforded time to produce a superb right-footed cross from the left and Rodriguez got in at the near post to head in.
Surprisingly the visitors could have been back in the game soon after when a cross from Joel Lynch found Miller but he headed wide from six yards.
Almost immediately Burnley went up the other end and Rodriguez could have had his hat-trick but he could not divert a shot on goal
Forest goalkeeper Lee Camp then made a superb save to keep out a volley from Austin before Burnley made the game safe in the 29th minute.
The visitors failed to clear their lines from Stanislas' corner and the ball fell kindly for McCann who stabbed home.
Four minutes later Forest squandered another gilt-edged chance as Matt Derbyshire shot wide from Miller's cross.
Burnley capitalised and a minute before the break Wes Morgan gave the ball away to Wallace who embarked on a mazy run before finding the bottom left-hand corner from the edge of the box.
With the game all but over Burnley slowed up after the break and Forest got one back in the 59th minute when Miller latched onto a long ball down the middle and squirmed a shot under Burnley goalkeeper Lee Grant.
Robbie Findley came agonisingly close to making it 4-2 when his shot cannoned off the post but Austin got the goal his performance deserved with 19 minutes left.
Burnley worked the ball out to Easton on the left and his deep cross found the former Swindon man who leaped superbly and looped a header over Camp and into the net.
Grant produced a superb save to deny Miller late on, and Lewis McGugan hit the post, but Burnley comfortably held on to keep McClaren under fire.