Jay Rodriguez opened his account for West Brom as Tony Pulis' side swept aside Accrington 3-1, transferring their Premier League form to the Carabao Cup.
After kicking off the campaign with 1-0 wins over Bournemouth and Burnley, the Baggies overpowered their League Two hosts, Salomon Rondon, Matt Philipps and Rodriguez all on target before Tom Dallison became the first player to score against them this season.
Rodriguez's display, capped with his rasping strike from 18 yards but also including a fine assist for the opener and plenty of neat touches in the final third, suggests a summer fee of around £12 million represents shrewd business, though sterner tests than this await.
Pulis suffered defeat by Northampton at the same stage last season and risked just four changes, Nacer Chadli returning despite continued transfer talk, but Manchester City target Jonny Evans was still out with hamstring trouble.
The visitors were quickly on the offensive, Rondon racing clear and drilling a shot at Aaron Chapman, who made the first of several saves.
But he had no chance of stopping the Venezuelan in the 11th minute, Rodriguez bending in the ammunition and Rondon heading powerfully into the bottom corner.
Accrington looked vulnerable to further damage, Ben Richards-Everton tripping over his own back pass to invite unwanted trouble and Rodriguez scuffing after finding space inside the area.
When they did muster something useful in response following a corner on the right, Jonny Edwards headed high and wide with only Boaz Myhill to beat.
Much of the remaining tension disappeared after 31 minutes when Stanley were caught cold from their own free kick, leaving an open invitation for Phillips to test his legs against them.
Rondon obliged with a long pass, with Phillips charging into the area and rifling clinically across goal.
Accrington reached the break at 2-0, but spent much of that time fighting for a foothold.
Home skipper Sean McConville did his best to summon a comeback, letting fly the first real chance of the second half from 30 yards and drawing a panicky save from Myhill, but it was not to be.
Instead the finishing blow came in cruel circumstances as Kayden Jackson, League Two's joint top-scorer with four, saw his penalty shout against Craig Dawson turned down, only for Albion to launch a counter-attack which ended with Rodriguez finishing from the edge of the area.
Accrington, spurred on by the energy of substitute Mekhi McLeod, gave their fans something to celebrate two minutes from time when Dallison slotted home, but the result was already in the bank.