This month's Nations League matches against Italy and Germany are the last opportunity for the Three Lions boss to work with his players before they meet up for the tournament in Qatar.
Toney scored seven times in 26 appearances for Town while on loan from Newcastle back in 2016-17.
The striker went on to have loan spells at Scunthorpe and Wigan before landing permanent deals with Peterborough and Brentford.
Southgate has named an expanded 28-man squad for England's challenging September double header, with Brentford sharpshooter Toney the headline inclusion.
The 26-year-old has never represented his county at any level and went on a myriad of loans before impressing at Peterborough and shining for the Bees.
Toney has scored five goals in Brentford's first six matches of the Premier League season - the same tally as England captain Harry Kane, whose Tottenham team-mate Eric Dier has been recalled.
The 28-year-old last won the last of his 45 caps in November 2020 and returns to the fold, as does Ben Chilwell for the first time since suffering a ruptured anterior cruciate ligament injury last November.
Fellow left-back Luke Shaw is also in the squad despite only playing two matches for Manchester United this season and dealing with a foot complaint.
Harry Maguire was also dropped to the bench by Erik ten Hag after defeats in the opening two games but the under-fire defender has been named in the England squad.
But United team-mates Jadon Sancho and Marcus Rashford are again omitted - the former is dealing with a muscle injury but the former is eye-catching given his impressive start to the campaign.
Dean Henderson - on loan at Nottingham Forest from United - returns to the fold following number one Jordan Pickford's injury, while Liverpool captain Jordan Henderson is out with a hamstring issue.
Euro 2020 star Kalvin Phillips is included despite concerns over a lack of playing time being compounded at Manchester City by a shoulder issue.
James Justin, Ben White and Conor Gallagher dropped out of the group that featured in June, while Tyrone Mings and Ollie Watkins are among those overlooked again.