In 2021/22, Mob reached the semi-final stage before losing 4-2 to Isle of Wight outfit Pan Community.
This season they defeated Southampton Leaguers Hamble United 4-2 to reach the last eight.
Defending MSL champions Burrfields lost 4-2 at Bisterne United Reserves, after a 1-1 draw, while Meon suffered a 6-5 loss at home to Ventnor, again after a 1-1 stalemate.
Goals from Mike Newman, Harry Potter, Rich MacDonald and Josh Bromback gave Mob victory on an artificial surface at Horndean Technology College.
Burrfields, who went out in the quarters to Mob last season, were left frustrated after having two first half goals ruled out for offside, including one in the opening five minutes from Laurie McIntosh.
A goal down at the interval, Burrfields were reduced to nine men for a period in the second half when McIntosh was sin binned after Charles Flatman went off with a shoulder injury.
The visitors levelled late on through Jordan Shuttleworth, whose effort was also flagged offside but, on this occasion, the referee overruled the linesman.
Bisterne scored all four of their spot-kicks in the shoot-out, while Shuttleworth and Richie Leader saw theirs saved.