Leicester produced a superb second-half display to overhaul the Ospreys and go top of their Heineken Cup pool.
Leicester (6) 30
Tries: B Deacon, Ellis, Chuter, Healey
Cons: Goode (2)
Pens: Goode (2)
Ospreys (12) 12
Tries: Parker, Cashmore
The Tigers were 12-6 behind at half-time after well-worked tries by Sonny Parker and Adrian Cashmore.
But in an enthralling contest at Welford Road, the home side constantly attacked after the break.
Brett Deacon cut the lead with his try before Harry Ellis, George Chuter and Austin Healey secured the win and a vital bonus point with a score apiece.
In the build-up to the game, all the talk was about Gavin Henson's first start of the season.
And he made an immediate impact when his inside pop pass to fellow centre Parker sent the Wales international over the line to score.
Andy Goode kept Leicester in the hunt with two penalties before the Ospreys went further ahead in first-half injury time through Cashmore.
Again Parker played a key role, this time linking with Richard Mustoe to send Cashmore darting over the line.
Leicester, though, were the more adventurous in the second half and were duly rewarded when Brett Deacon pounced after some sustained forward pressure in the 54th minute.
That took them one short of their Welsh rivals' total and, five minutes later, into the lead when Ellis, who will have impressed England's management with a blistering display, broke clear to launch himself over the line.
The win was then effectively sealed when Chuter scored - again from close range - with less than 10 minutes left on the clock.
With the prospect of a vital bonus point - for scoring a fourth try - Leicester battled to the final whistle.
And it paid off - once more courtesy of their pack - when Healey dived at the back of a maul for a try of his own.
Leicester head coach Pat Howard: "We focused a bit more up front in the second half.
"But I thought their finishing was a bit more clinical than ours. We had to work had for our opportunities.
"The bonus point is important, and we know it will be crucial in the end. We know (the group) is going to be tight."
Ospreys head coach Lyn Jones: "You have to take your opportunities and you don't get many in games like this.
"Leicester were a bit more thorough than us. They got a bit more excited when they broke through.
"We had opportunities to score some more points in the first five minutes and didn't take them and if you don't win your own line-out ball, you are going to struggle."
Leicester: Vesty; Lloyd, Smith, Cornwell, Murphy; Goode, Ellis;
Moreno, Chuter, Morris; L Deacon, Kay; B Deacon, Jennings,
Replacements: Healey for Lloyd (50), Broadfoot for Goode (80), Hipkiss for Ellis (76), Buckland for Chuter (80), Holford for Morris (71), Abraham for Jennings (80).
Not used: Cullen.
Ospreys: Cashmore; Terblanche, Parker, Henson, Mustoe; Connor,
Spice; D Jones, B Williams, A Jones; Newman, Evans; Bater,
Replacements: S Williams for Cashmore (64),
M Jones for Connor (74), Bennett for B Williams (64), Millward for A. Jones (69).
Not Used: Bateman, Beech, A Bishop.
Ref: Joel Jutge (France).