The scrappy pattern of the first half continued into the second with the shrill blast of Michael Oliver’s whistle observing a steady stream of fouls.
The Loftus faithful were growing ever more obstreperous as their team failed to muster a serious chance on goal.
With four minutes remaining, finally it came but Toni Leistner somehow contrived to miss the target from a yard out after Darnell Furlong had smashed the ball across goal.
The Hornets hung on and went to bask in the acclaim of their 2654 fans who were already singing of Wembley.
QPR: Lumley; Furlong, Leistner, Hall (Osayi-Samuel 84), Wszolek (Eze 76), Luongo, Cousins, Freeman, Bidwell; Wells (Hemed 71), Smith. Subs: Ingram, Scowen, Manning, Kakay.
Watford: Gomes; Janmaat, Kabasele, Britos, Holebas; Hughes, Capoue; Cleverley (Quina 84), Sema (Mariappa 74); Gray (Doucoure 74), Deeney. Subs: Dahlberg, Deulofeu, Penaranda, Navarro.
Booked: Mariappa, Doucoure
Referee: Mike Oliver