Steam-Baked Summer Squash

2 lb summer squash sliced 1/4 inch thick

1/2 c. chopped onion

1/4 c. chopped red pepper

1/4 chopped green pepper

4 T. unsalted butter, melted

2 cloves garlic, minced

3/4 t. kosher salt

1/4 t. ground pepper

Preheat oven to 325 degrees F. Coat a 9x13 inch baking dish with cooking spray. Combine squash, onion, red and green bell pepper, butter, garlic, salt and pepper in a large bowl. Transfer to the prepared pan and cover with foil. Bake until the vegetables are very tender, about 45-55 minutes. Serves 6.