Leicester guaranteed top spot in the Premiership and secured a home play-off semi-final with a comfortable win over Harlequins at Welford Road.
The Tigers trailed 17-16 at half-time, Toby Flood's early try cancelled out by tries from Danny Care and George Lowe.
But the hosts came storming back after the break, with Matt Smith and Ben Youngs both crossing and a penalty try putting them out of sight.
Joe Marler added a late try for Quins, but it was too little, too late.
Northampton's defeat at the hands of third-placed Saracens means Leicester lead Saints by six points with one game remaining, the visit of Sarries in a fortnight.
Leicester were ahead within three minutes, Quins winning a line-out on halfway only for Care's pass to be neatly intercepted by Flood, who raced away to score.
The outside-half added the conversion and, minutes later, a 30-metre penalty to compound the visitors' nightmare start.
From a scrum, Care made amends for his earlier error by breaking, kicking ahead and winning the race for the touchdown, with the Leicester defence strangely hesitant. Rory Clegg converted to make it 10-7 after 10 minutes.
With 15 minutes gone the visitors were penalised at a scrum but Flood was unable to take advantage, but the Tigers maintained the pressure when Flood kicked another penalty after 23 minutes.
Quins were struggling to stem the attacking verve of the Tigers, with the visitors giving away frequent penalties, and a yellow card seemed on the cards as they continued to offend.
Flood added another simple penalty, but Quins then produced a 10-point scoring burst to give them a surprising 17-16 interval lead.
Firstly David Strettle and Care combined to send Lowe away for a try which Clegg converted, before Lowe produced a strong run to set up a ruck in the home 22 from which Clegg put his side ahead with a neat drop-goal.
Leicester began the second half strongly, with both wings coming close in the opening moments before the referee's patience was finally exhausted and he sent Quins flanker Chris Robshaw to the sin-bin.
Flood kicked the resulting penalty and minutes later added the conversion to a try from Matt Smith after Johne Murphy had produced a splendid run to set it up.
Robshaw's absence proved costly for his side as Leicester extended their lead when Youngs took a quick tap penalty to score, with Flood converting to give Leicester a 33-17 lead after 50 minutes.
Robshaw returned but still his side had difficulty in breaking out of their half, with Flood narrowly denied after an excellent break.
The one-way traffic for the Tigers and the crippling penalty count for Quins continued and, after a succession of scrums in the visitors' 22, Leicester were awarded a penalty try to secure a bonus point.
Flood converted to give him a match tally of 20 points, before replacement hooker Marler picked up a consolation try at the death.
Leicester coach Richard Cockerill: "It's very pleasing to finish top... but we haven't won anything yet so we have to keep focused.
"We kicked poorly [in the first half], dropped off tackles and they had the quality to take advantage.
"I'm disappointed we conceded three tries. We had to keep our composure, we were a little bit rattled."
Harlequins director of rugby Conor O'Shea: "We were magnificent and if we can continue to play with that intensity we'll finish in the top four next season.
"If you come to a place like this you know decisions will go against you.
"At 10-0 down we didn't throw in the towel and the loss of Chris Robshaw to the sin-bin was crucial."
Leicester: G. Murphy, Hamilton, M. Smith, Allen, J. Murphy, Flood, B. Youngs, Ayerza, Davies, Cole, Parling, Kay, Croft, Moody, Newby.
Replacements: Amorosino for G. Murphy (60), Staunton for Flood (72), Grindal for B. Youngs (72), Stankovich for Ayerza (66), Chuter for Davies (72), Castrogiovanni for Cole (56), B. Deacon for Kay (56).
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