QPR needed penalties to avoid an upset in the Carabao Cup and reach the second round after eventually beating Leyton Orient 5-3 in a shoot-out.
Rob Dickie’s second goal in consecutive matches appeared to put the Championship side on course for a routine victory.
However, Orient recovered and Aaron Drinan levelled late on before Ruel Sotiriou’s missed effort from 12 yards saw the O’s exit the competition.
In Tuesday night’s games, George Saville scored his first goal back at Millwall as the Championship side came from behind to defeat League One outfit Portsmouth 2-1.
Reeco Hackett-Fairchild gave Portsmouth the perfect start when he seized upon a sloppy pass before running into space and slamming a shot into the bottom corner in just the fourth minute.
But Millwall recovered from that early blow to level after 21 minutes when Jed Wallace’s shot was pushed out by Pompey goalkeeper Alex Bass into the path of Scott Malone, who tucked away the rebound.
And Saville put the Lions’ ahead six minutes later with what proved to be the winner against a Portsmouth side who had defender Callum Johnson sent off just after half-time.
Meanwhile, Sutton United’s first EFL Cup tie ended in a 3-2 defeat at Championship Cardiff despite taking an early lead through Donovan Wilson.
Marley Watkins’ double either side of the break turned the tables in Cardiff’s favour before Josh Murphy added a late third and Coby Rowe grabbed a late consolation.
And finally, Paul Osew hit the winner as AFC Wimbledon booked their place in the next round with a 1-0 win at south London neighbours Charlton Athletic.
SECOND ROUND DRAW (Southern Section, London ties)
Brentford vs Forest Green Rovers
Millwall vs Cambridge United
West Bromwich Albion vs Arsenal
Birmingham City vs Fulham
QPR vs Oxford United
Northampton Town vs AFC Wimbledon
Watford vs Crystal Palace
Ties to be played week beginning August 23.