The Red Devils burst out of the blocks in a Premier League fixture at Vicarage Road, netting three times inside the opening 45 minutes.
Ashley Young bagged a brace against his former club to put Jose Mourinho’s side on their way, before Anthony Martial also got in on the act.
The last time United found the target three times in the first-half of a Premier League fixture was against Swansea on November 6, 2016.
On that occasion, Zlatan Ibrahimovic bagged a brace after seeing Paul Pogba open the scoring.
The Red Devils went on to win that game 3-1, with the damage done early on at the Liberty Stadium.
Collecting another three points in their latest outing against Watford will help to keep Mourinho’s men on the heels of arch-rivals Manchester City in the battle for English top-flight supremacy.