WINDSOR, England (AP) _ Thousands of sightseers crowded Wednesday onto the grounds of Frogmore cemetery at Windsor Castle for the first public view of the Duchess of Windsor's grave, a mound of dark earth marked by a simple oak cross and a bunch of white lilies.

''I don't think we have ever seen quite so many people here,'' said Amanda France, administrator of the National Garden Scheme. It opens Frogmore to the public only one or two days a year to raise money for nurses' charities and the National Trust.

This was the first open day since the duchess was buried April 29 beside the Duke of Windsor, who abdicated as King Edward III in 1936 to marry her. He died in 1972.

The duchess, twice-divorced Baltimore socialite Wallis Warfield Simpson, died in Paris on April 24 at 89.

The masoleum where Queen Victoria is buried and the graves of several of her children and grandchildren also were on view Wednesday, but it was grave No. 24, where the duchess is buried, that the crowds came to see.

Andrew Jackson, the superintendent of parks at the castle 22 miles west of London, said the grave, in the shadow of a large plane tree, would be allowed to settle for about three months before a stone is placed on it and forget-me- nots are planted.

The stone and flowers will match those of the duke's grave less than a foot away.

The royal family, which shunned the duchess for much of her life, honored her in death by holding her funeral in St. George's Chapel at the castle before 175 royals, dignitaries and friends and allowing her burial beside the duke.

Michael Shea, the queen's press secretary, said at the funeral that the inscription on her grave would read, ''Wallis, Duchess of Windsor 1896-1986.''

It will not be marked with the initials HRH, for Her Royal Highness, the title traditionally given to the wives of royal dukes. Queen Elizabeth II refused the duke's wish that she be given the title.

Members of the public paid about $1 to enter the grounds and were not allowed to come closer than 20 yards to the grave. Few seemed to have much sympathy for her.

''I don't see any reason why she should have HRH on her tombstone,'' said Alfreda Ottewell, 72, of Bracknell. ''On the other hand, I think the Windsors' marriage and his abdication was good for the country because we got a better king as a result.''

Queen Elizabeth's father, King George VI, became king when his elder brother renounced the throne.

Jim Bernardi of Reno, Nev., said it was right for her to be buried at Frogmore but that it would be ''hypocritical'' to put a title on her grave that had been denied her during life.