In 1947 when it didn't look like there'd ever be any other Marx Brothers movies, Groucho appeared sans siblings in a film called Copacabana. It wasn't a very good film, nor was Love Happy which featured Groucho, Chico and mostly Harpo a couple of years later. But Copacabana did have about six minutes of Groucho near his prime and I've embedded them below.
This clip is a tiny bit outta sync but trust me, this is still better than sitting through the whole movie…