Marcus Rashford and Barkley had Gareth Southgate's men two goals to the good midway through the first half when play was stopped and a message relayed over the public address system at Vasil Levski National Stadium, urging home supporters to cease their abuse.
In between Barkley and Sterling continuing an emphatic response to the Three Lions' surprise defeat to the Czech Republic, there was a further lengthy delay.
The game appeared under threat of abandonment at that stage, as a group of fans were ejected, but England resumed their punishment of over-matched opponents – captain Harry Kane laying on Sterling's second and completing the scoring five minutes from time.
Manchester United's Rashford, who has struggled for form at club level this season, left Georgi Pashov on the turf before thrashing into the top corner from a tight angle in the seventh minute.
Jordan Pickford got down sharply to keep out a 25-yard drive from Bulgaria captain Ivelin Popov, although that amounted to a fleeting moment of encouragement for the hosts.
Sterling played a slick one-two with Kane and drilled across the face of goal for Barkley to tap home in the 20th minute.
Barkley's second, a finely judged run and header to meet Kane's curling cross, came after the first stoppage in play.
Southgate was in discussion with the fourth official shortly before half-time when the game was halted again and a group of Bulgaria fans were escorted out of the stadium.
Unperturbed by the dismal circumstances, Kieran Trippier and Kane combined for Sterling to make it 4-0 at the interval.
The one-way traffic continued after the break, with Sterling slotting wide before he and Kane got in one another's way.
Plamen Iliev then foiled the Manchester City forward with his boot but he would not be denied a seventh goal in qualification when Kane teed him up 21 minutes from time.
The Tottenham striker dispatched a shot beyond the beleaguered Iliev to get the goal his efforts deserved, while substitute Callum Wilson hit the post as Bulgaria downed tools.
What does it mean? UEFA must act
The sight of Sterling scoring to make a mockery of those abusing him and his team-mates felt inevitable. We know all about the unbending fortitude of this admirable 24-year-old when faced with such vile incidents. But it is time he and England's other black players – such as Tyrone Mings, who might find an international debut played out amid such sickening vulgarity hard to cherish – were able to be confident they might never ply their trade in such circumstances again.
Bulgaria head coach Krasimir Balakov attempted deflection and whataboutery pre-match. Sadly, this is not a problem exclusive to his country – far from it – but the authorities must now take a strong stance and make an example of them. Football has paid lip service to tackling racism for far too long.
Barkley banks some timely credit
Before the match, former Manchester United midfielder Roy Keane questioned Barkley's effectiveness in terms of goals and assists. Those are unfortunate queries for a career attacking midfielder to have hanging over him and Barkley grasped his recall clinically.
Chelsea team-mate Mason Mount and James Maddison are among Southgate's latest call-ups, while Jack Grealish and Phil Foden might also come into the reckoning soon. It meant this was a timely reminder of the ex-Everton favourite's qualities.
Pashov a pushover
It always promised to be a tough outing for a Bulgaria side swatted aside at Wembley last month and they could have done without Pashov's efforts preceding Rashford's opener. The right-sided defender headed Harry Maguire's long ball straight to Barkley and his attempts to remedy the situation were more akin to Sunday League football.
Key Opta Facts
- England have faced Bulgaria without losing more times than they have any other opponent in their history (P12 W8 D4 L0).
- England have scored at least five goals in four different matches in 2019, their joint-most in a single calendar year (also in 1937 and 1908).
- All six of Barkley’s goals for England have been away from home – only Freddie Steele (8) and James Windridge (7) scored more for the Three Lions without netting at home.
- Sterling has been directly involved in 13 goals in qualifying (eight goals, five assists). Only Russia's Artem Dzyuba has been involved in more (14).
- Kane has been directly involved in 15 goals in his past 10 games for England in all competitions (nine goals, six assists).
England host Montenegro before closing out the campaign in Kosovo, with qualification seemingly a formality. The Czech Republic travel to face bottom-of-the-table Bulgaria, whose reckoning must now be with UEFA.