Lightly brown bacon in large (3 qt) saucepan.

Stir in onions when bacon is browned and cook over medium heat until clear.

Add sliced summer squash and mix with bacon and onion.

Allow squash to cook down stirring often.

Grease large casserole dish on all sides.

When squash is cooked, spoon out enough to cover bottom of casserole dish to about 2 inches with slotted spoon.

Put 5 or 6 pats of butter and several dollops of sour cream or cream cheese (sour cream is easier to work with) on top of layer and cover with bread crumbs.

repeat process with second layer, but do not put sour cream or cream cheese on top of casserole.

Put casserole into 325 degree pre-heated oven uncovered and cook for 1 hour.