What company does Clark W Griswold work for?
The only hint to the name of the company that I can find is in Christmas Vacation. In a scene where Clark is in his office, you can see awards for "Designer of the Year" given to Clark from the Society of Food Additives. I doubt that would be the name of the company he works at, but who knows?
With Christmas only a few weeks away, long-time Chicago resident Clark W. Griswold (Chevy Chase) decides it's time to get a Christmas tree. He gathers his wife Ellen (Beverly D'Angelo), daughter Audrey (Juliette Lewis) and son Russ (Johnny Galecki) into the family station wagon and drives out to the country where he finds the perfect tree. Since Clark has brought neither axe nor saw, the tree is pulled from the frozen ground.