The midfielder, who under former Blues' boss Carlo Ancelotti enjoyed a number of appearances in the Premier League and in Europe, has slid down the pecking order at Stamford Bridge in recent seasons.
Now 21, McEachran's most recent experiences have come in the Championship while on loan at Middlesbrough, Watford and Wigan, and he is currently training under Southgate ahead of Monday's European Championship qualifier against Wales.
He is also part of the U21 squad for the forthcoming tournament at Toulon in France and Southgate - team manager - said: "He is a player that we know can use the ball. He has ability on the ball.
"The way we want to play is through midfield so you need midfield players that can handle possession and Josh is a good footballer technically.
"Hopefully, the opportunity to come and train with us rekindles a fire for them because young players can be hit in terms of their confidence when progress is not always in an upward direction.
"We are hoping Josh being with us this week sets him up with renewed enthusiasm for next season because we know what talent he has got."