José Froilán González won the very first WDC race for Ferrari in Silverstone 1951, having driven for Talbot Lago the season-opener.
J-M Fangio won the 1954 French GP in a Mercedes-Benz, having won the two previous WC GPs for Maserati.
Stirling Moss won three races 1957 fpr Vanwall after he drive the season opener for Maserati.
Stirling Moss won three races 1958 for Vanwall after he won the season opener in Argentinia in a Rob Walker Cooper Climax.
Tony Brooks won the German Grand Prix 1959 for Ferrari after having competed a one-off for Vanwall the race before.
John Surtees won the 1966 Mexican GP in a Cooper, having moved to Cooper from Ferrari in mid-season.
Peter Gethin won the 1971 Italian GP for BRM, having driven for McLaren for most of the season.
Ronnie Peterson won the 1976 Italian GP for March, having moved from Lotus after the first WC GP of the year.
Mario Andretti won the 1976 Japanese Grand Prix for Lotus, having driven for Parnelli earlier in the season.
Max Verstappen won the 2016 Spanish Grand Prix for Red Bull, having driven for Toro Rosso realier in the season.