I have great news about picture book query letters: they can be extremely short and simple! Many authors agonize over query letters for novels and memoirs because they are key in convincing an agent to read a whole book. Picture books, on the other hand, are so short that agents are likely to at least skim the whole book as long as the query letter is half-decent. Back when I was an agent intern going through query letters, that’s certainly what I did.
Of course, you should still carefully compose a solid query letter, but much of the advice you’ll find online about query letters is geared toward longer books. So, here’s my take on writing a picture book query letter (with an example of my own successful letter).
Follow the basic template you’d use for any book: the hook, the book, and the cook.