There have only been four instances in the history of a Formula 1 that a team has won its debut race. It has happened in 1950 with Alfa Romeo, 1954 with Mercedes, 1977 with Wolf Racing and 2009 with Brawn.
Motor racing resumed after World War II and the British Gand Prix was the first of the seven races in the 1950 World Championship. It is natural to have a debut win in the very first race of the first World Championship Formula One race in the modern era. The 70-lap race was won by Giuseppe Farina for the Alfa Romeo, after starting from pole position. Teammate Luigi Fagioli finished second and Reg Parnell took the last step on the podium in a third Alfa Romeo for a unique 1-2-3 on the podium for the side from Turin, Italy.
The next instance of a debut race win came four years later. Formula 1 switched to 2.5 litre engines for 1954, and Mercedes had re-entered Grand Prix racing for the first time since post-war at the French Grand Prix with Juan Manuel Fangio and Karl Kling taking to a 1–2 win at the very first race for them. The Argentine Fangio had earlier rode for Maserati in the first 3 races and won in Buenos Aires and Spa, before switching to the Silver Arrows.
Canadian squad Walter Wolf Racing won the very first race they entered in 1977 with South African driver Jody Scheckter, after a deeply attritional race that saw only seven out of the 21 racers finishing. Based out of Reading, the team was owned and run by Walter Wolf and competed in 3 seasons, from 1977-79 in Formula 1.
The final instance, of course, is the sensational victory by Jenson Button for Brawn Grand Prix in 2009 after the team was formed just days ahead of the beginning of the season. Button led a 1-2 finish for Brawn with team-mate Rubens Barrichello.