The hugely influential Angel Di Maria scored on his home debut as United ended the wait for a first competitive win under the Dutchman in style, with Ander Herrera, Wayne Rooney and Juan Mata also on the scoresheet.
Radamel Falcao, who completed a season-long loan move from Monaco on transfer deadline day, was introduced as a second-half substitute for his first appearance in a United shirt, while Van Gaal fielded two other new faces, Marcos Rojo and Daley Blind, from the start.
However, although Van Gaal was impressed with the manner in which QPR were dispatched, he remains keen to see more from a United side that has been rebuilt following a disappointing seventh-place finish last season.
"When you have a result of 4-0 then you can be happy as a coach but you always have points you can improve," said the 63-year-old.
"I am very happy because of the result and the way we have played. We were very dominant and scored goals and kept a clean sheet.
"In ball possession I think we have lost the ball too much previously. We were more direct and that I like.
"Also, we have created a lot of chances, although we didn't score enough of them.
"We have always to analyse what we have done. The result is fantastic but we can get much better. This is a good start."
