Match ends, West Bromwich Albion 0, Leicester City 3.
Jamie Vardy scored a second-half penalty double as Leicester condemned West Brom to a disappointing return to the Premier League.
After goalkeeper Sam Johnstone twice came to the home side's rescue with saves to deny Harvey Barnes in the first half, new signing Timothy Castagne broke the deadlock when he nodded home a far-post cross from fellow Belgian Dennis Praet nine minutes after the restart.
Vardy, last season's Premier League top scorer, then got up to score from the spot after being dragged back by Kyle Bartley as he chased into the box to support a move that saw Johnstone deny former Baggies loanee Barnes for a third time.
The 33-year-old repeated the feat 10 minutes later after Dara O'Shea tripped James Justin.
As playmaker James Maddison made a second-half appearance off the bench after recovering from a hip operation that crucially caused him to miss the end of the season, it was a good day for manager Brendan Rodgers and his team, who were winning this particular fixture for the fifth time in a row.
For West Brom, it was a brutal reminder of the task they face merely trying to stay in the top flight.
All three promoted teams lost on the opening weekend and - like Fulham, who were beaten by a similar scoreline against Arsenal on Saturday - there are early question marks over whether they have the quality to survive.
Good day for Leicester
Leicester's biggest away win since New Year's Day provided a positive response to some major questions.
After looking like Champions League certainties for the first half of the season, a draining run of 17 games in which they claimed only four wins and 17 points saw Leicester overtaken by Manchester United for a top-four spot on the final day of the season.
Just as his side's form nosedived, so did Vardy's.
He may have been the Premier League's top scorer but 17 of his 23 goals came before Christmas Day.
After toiling for most of the afternoon, Vardy's day seem to be reaching an unhappy end when he limped away from a collision with Johnstone.
But the physio sorted Vardy out and within minutes he had scored. Ten minutes after that, he had another one.
The similarity of his penalties was uncanny. The run-up was purposeful, the shot powerful, both times to Johnstone's right as the keeper dived the wrong way to his left.
"Any team would want him. He's super cool, clinical, still has pace and running ability," said Rodgers.
"He's a box player. He'll never be dropping underneath with bright intricate play but he's a killer in the box. Whether from a cross or penalty he's got the eye to score. He never looked like missing."
Maddison's introduction was further reason for Leicester to cheer, although with a notoriously draining Europa League campaign to negotiate from the middle of October, it is fair to assume Rodgers will want more signings beyond Castagne, who has been brought in as a replacement for Ben Chilwell, who joined Chelsea for £45m.
"There is a load of work going on behind the scenes. We will see what happens in the next few days," added Rodgers.
"Delighted with the guys who are here. We will try to improve this squad whether we get new players in or not."
When West Brom went down three seasons ago, their measly 31 goals was one of the major reasons.
Salomon Rondon and Jay Rodriguez were joint top scorers with seven, so it is obvious where the Baggies must improve if they are to stand a chance of preserving their Premier League status.
Having spent £28m on three new attackers - all of whom joined on a more permanent basis after impressing during the club's promotion season - expectations around Pereira, Grady Diangana and Callum Robinson are high.
There was evidence of plenty of movement from the three of them but it only translated into a single shot on target.
Kasper Schmeichel made one feet-first save from Pereira before the break but the Brazilian's effort was going wide anyway. Pereira was the home side's major attacking threat - and might have done better with a volley he sent sailing over the bar after controlling in a good position inside the Leicester box.
But without a greater goal threat, it could be a long old season for the Baggies.
"I was really pleased with the way we played until they scored," said Albion boss Bilic.
"It was a good performance up to then, with and without the ball. Very disappointed with the result. Our mentality was not the same after the goal. We have to think forwards."
Man of the match - Timothy Castagne (Leicester)
Vardy equals Van Nistelrooy record - the stats
- Leicester have won all five of their Premier League away games against West Brom - no other side has a better 100% away win rate against an opponent in the competition (Man City also 5/5 vs Bournemouth and Arsenal 5/5 vs Hull).
- All three promoted clubs (Leeds, West Brom and Fulham) have lost their opening match of a Premier League campaign for the first time since 2013-14, when Crystal Palace, Hull and Cardiff did so.
- The home side remains winless in all nine Premier League meetings between West Brom and Leicester (D2 L7), with only Bournemouth v Watford (10) being played more without the home side winning.
- Leicester earned their first Premier League away win since New Year's Day (3-0 at Newcastle), ending a run of eight games without a win on the road (D3 L5).
- In 380 Premier League games last season, there was just one occasion of a player scoring two penalties in a single match (Troy Deeney v Newcastle) - it's happened twice already in five matches this season (Mo Salah v Leeds, Vardy for Leicester).
- Vardy has scored in all five of his away Premier League appearances against West Brom, equalling Ruud van Nistelrooy's record of most away games vs an opponent in the competition with a 100% scoring record (5/5 at Newcastle).
- Leicester's Castagne became the fifth different Belgian player to score on his Premier League debut, after Luc Nilis, Thomas Vermaelen, Christian Benteke and Leandro Trossard.
- Leicester's Vardy became the first player to score two penalties in an away Premier League game since Riyad Mahrez vs Everton in December 2015 - also for Leicester.
West Brom play EFL new boys Harrogate Town in the Carabao Cup second round on Wednesday before travelling to Everton in the Premier League on 19 September (12:30 BST). Leicester do not enter the EFL Cup until the third round. Their next game is at home to Burnley, live on BBC One, on 20 September (19:00).
- 2FurlongSubstituted forHarperat 69'minutes
- 6AjayiBooked at 63mins
- 12Costa Pereira
- 19SawyersSubstituted forEdwardsat 68'minutes
- 7RobinsonSubstituted forRobson-Kanuat 60'minutes
- 2JustinBooked at 16mins
- 17PérezSubstituted forAlbrightonat 67'minutes
- 26PraetSubstituted forMaddisonat 75'minutes
- Anthony Taylor
- Shots on Target
Second Half ends, West Bromwich Albion 0, Leicester City 3.
Attempt missed. Hal Robson-Kanu (West Bromwich Albion) left footed shot from outside the box is too high. Assisted by Grady Diangana.
Attempt blocked. Kyle Edwards (West Bromwich Albion) right footed shot from the centre of the box is blocked.
James Maddison (Leicester City) wins a free kick on the left wing.
Foul by Semi Ajayi (West Bromwich Albion).
Goal! West Bromwich Albion 0, Leicester City 3. Jamie Vardy (Leicester City) converts the penalty with a right footed shot to the bottom left corner.
Penalty Leicester City. James Justin draws a foul in the penalty area.
Penalty conceded by Dara O'Shea (West Bromwich Albion) after a foul in the penalty area.
Attempt missed. Harvey Barnes (Leicester City) right footed shot from the left side of the box is close, but misses to the right. Assisted by James Maddison.
Corner, Leicester City. Conceded by Jake Livermore.
Youri Tielemans (Leicester City) wins a free kick in the defensive half.
Foul by Matheus Pereira (West Bromwich Albion).
Substitution, Leicester City. James Maddison replaces Dennis Praet.
Goal! West Bromwich Albion 0, Leicester City 2. Jamie Vardy (Leicester City) converts the penalty with a right footed shot to the bottom left corner.
Penalty Leicester City. Jamie Vardy draws a foul in the penalty area.
Penalty conceded by Kyle Bartley (West Bromwich Albion) after a foul in the penalty area.
Foul by Timothy Castagne (Leicester City).
Grady Diangana (West Bromwich Albion) wins a free kick in the attacking half.
Nampalys Mendy (Leicester City) wins a free kick in the defensive half.