EZRA JACK KEATS, 67, IS DEAD; ILLUSTRATED BOOKS FOR CHILDREN

Ezra Jack Keats, an illustrator and writer of children's books who won many awards, died of a heart attack early yesterday at New York Hospital. He was 67 years old.

Mr. Keats illustrated 33 books, 22 of which he also wrote. Most of them were for preschoolers. He won a Caldecott Medal in 1963 for what is probably his best-known tale, ''The Snowy Day,'' published by Viking Press. A movie adaptation of the picture book won a prize at the Venice Film Festival two years later.

The book told the story of Peter, who samples the delights of winter, crunching snow underfoot, making tracks, building a snowman, saving a snowball - and getting his feet wet. A reviewer in The New York Times called it ''a gentle story that tells its action eloquently in few words and in the frosty blues and other beautifully combined colors of outstanding illustrations.'' Designed Sets and Costumes

''The Trip'' (1978), about a boy who moves out of Peter's neighborhood, has just been adapted for the First All-Children's Theater, 37 West 65th Street, with lyrics and score by Stephen Schwartz, and is to be performed for a two-week ''sneak preview'' starting May 12 prior to a Halloween opening. Mr. Keats had just completed designing the sets and costumes.

His style as an illustrator was marked by swirls of color. He often used a collage method, combining different kinds of paper, many of them marbleized and many of which he made himself. He also worked in acrylics.

Mr. Keats did meticulous research for his books, and would search for just the right child to model a certain costume. In ''Hi, Cat!,'' a story about Halloween paper-bag costumes, which won an award from The Boston Globe in 1970, he drew puppets that he had made himself. Grew Up in Brooklyn

Mr. Keats, who grew up in Brooklyn, went to Paris for a year to paint after serving in the Army in World War II. He returned to New York to live in Manhattan, where he continued to paint and began to illustrate books.

His own books have been translated into 16 languages. In 1974, a roller-skating rink was built in his honor in Tokyo in response to the enthusiasm that greeted the Japanese translation of his ''Skates!''

Among his other awards was a Caldecott Honor in 1970 for ''Goggles!,'' and a Gold Venus Medallion at the Virgin Islands International Film Festival in 1977 for the film version of ''Apt. 3'' Mr. Keats also designed five Christmas cards for UNICEF.

Surviving is his brother, William. A funeral service will be held at noon tomorrow at the Riverside Chapel, Amsterdam Avenue and 76th Street.