Preheat your oven to 400 degrees. Place squash and onion in a large skillet & pour in enough water to cover. Turn the heat on medium-high, cover, & cook until tender – about 5 minutes. Drain well, and place in a large bowl. Set aside.

In a small bowl, whisk together the eggs, milk, butter, salt, & pepper. In another bowl, mix together the crumbled cheese crackers & the cheese. Stir half of the crumb mixture into the squash along with the egg mixture. Combine well. Pour into a 2 to 3 quart casserole dish, and top with the remaining cracker/cheese mixture. Bake for 30 minutes.