preheat oven to 350.
heat olive oil in large skillet over medium- high heat. Add onion and mushrooms; cook 5 - 7 minutes . Add garlic; cook an additional 30 seconds. Reduce heat to medium-low, add all but 1/2 cup tomatoes and simmer 5 minutes. Remove from heat.
Stir together ricotta cheese, parmesean, italian seasoning, eggs, and 1/2 cup Mozzerella cheese.
place remaining tomatoes in a greased 9 x 13 " baking pan. Layer 1/2 of the squash slices on top of the tomatoes. Spread ricotta mixture over squash evenly with the back of the spoon. Sprinkle 1/ 2 cup Mozzarella over Ricotta Mixture.
Repeat the squash and cheese layers.
Cover with aluminum foil sprayed with cooking spray. Bake 35 minutes. Uncover; bake an additional 20 to 25 minutes or until squash is tender. Let stand 20 minutes before slicing and serving.
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