My favorite way to cook summer squash is to saute a sliced sweet onion like Wallawalla in a little butter&olive oil in a wok.  The olive oil keeps the butter from burning and the butter adds flavor.  When it is soft add a few leaves of chopped fresh sage (bergartenor holts mammoth are my preferred varieties) and cook for a couple minutes.  Add two or three small summer squash depending on the number of people you are serving  (I like using yellow and greeen mixed) that have been sliced in 1/4 inch slices, add enough chicken broth that won't quite cover the mixture and cook just till squash is tender which will take about 3- 4 minutes.  Don't overcook. Finish with salt and freshly ground pepper.