United beat last year’s Vase winners Newport Pagnell Town 1-0 with substitute Kai Walters scoring the winner 10 minutes from time in his last game for the club before moving to Australia.
Forster also helped Ascot to win the Combined Counties Premier Division North title, earning them promotion to the Isthmian League South Central Division.
He went on loan to the club following an injury to Jamie Ashdown, the former Reading and Portsmouth stopper who is also Ascot’s goalkeeping coach.
Forster will have benefited from Ashdown’s coaching and is now hoping to regain a regular first-team place with the Rebels.
*EBFL Division 1 champions Stoke Poges suffered their first league defeat of the season when they lost 4-1 to second-placed Sandhurst Town Reds, their only goal coming from Sam Manton.
Cressex stayed third in the placings following a 4-3 win over Old Windsor Reserves with goals from Jack Knight (2), Andre Labuschagne and Jack Low, while Frontline Reserves remain fourth despite losing 2-1 to Sandhurst.
Stoke Poges lost 2-0 to Reading YMCA Rapids in the Maidenhead Norfolkian Junior Cup final at Burnham on Wednesday.
The Senior Cup final may not be played this season due to an investigation into the semi-final which saw Britwell beat Reading City U23s 3-2.
City claimed Britwell fielded an ineligible play but, after looking into the matter, the cup committee allowed the result to stand. However, the Reading club appealed against that decision and it is now in the hands of the Berks & Bucks FA. The final could be held over to early next season.
Old Windsor Reserves won the Ascot & District (Fielden) Cup by beating Singh Sabha 4-3 on penalties after last Friday’s tie had ended 3-3. Jude Van-Spall, James Walton and Lewis Corney scored for Windsor with Pavandip Kang, Pritpal Raju and Alpha Sesay on target for the runners-up.
Singh Sabha are heading for the final of the Roy Lester Cup following a 5-2 win over Pobbers with their goals coming from Hasan Mahmood (2), Bobby Samra, Jas Samra and Naheer Nawaf.