Langsford was first out after failing to impress host Marco Pierre White following the celebrities' initial culinary challenge.
The remaining stars then attempted to each cook a set menu for 25 paying diners. All three contestants faced a score out of 100, which was decided by both the customers and White.
Dorgu went home after scoring 52 points, below Ferns's 55 and Dell'Olio's 53. White then picked Ferns to go through due to his "competitive spirit".
"I just want to win this thing now!" Ferns said afterwards.
Next week's semi-final will feature Elen Rives, Debra Stephenson, Donna Air and Russell Grant.
Marco's Kitchen Burnout continues next Friday at 9pm on ITV1.