Heat the olive oil in a large pan over medium heat. Add the onions and carrots and cook for 3-4 minutes.
Add the zucchini, yellow squash and red bell pepper to the pan. Cook for an additional 5-6 minutes or until vegetables are tender.
Add the spinach to the pan. Cook, stirring occasionally, for 2-3 minutes or until spinach has wilted. Season the vegetables with salt and pepper to taste.
Add the garlic, and cook for 30 seconds. Pour the marinara and tomato sauces into the pan, then bring to a simmer.
Cook the sauce for 10 minutes.
While the sauce is simmering, prepare the cheese filling.
Place the ricotta, eggs, parmesan, 1 cup mozzarella, salt, pepper and Italian seasoning in a large bowl. Stir to combine.
Cook the lasagna noodles according to package directions.
Preheat the oven to 375 degrees F. Coat a 9"x13" pan with cooking spray.
Spread a small amount of sauce on the bottom of the pan. Add a layer of noodles, then spread 1/2 of the cheese mixture over the noodles.
Top the cheese mixture with 1/3 of the vegetable sauce.
Repeat the layers, ending with the vegetable sauce.
Cover the lasagna with foil, then bake for 45 minutes.
Uncover the lasagna, then add the remaining 2 cups for mozzarella cheese. Bake for an additional 15 minutes or until cheese is melted and browned.
Sprinkle lasagna with parsley. Let stand for 5-10 minutes, then cut into slices and serve.