Preheat oven to 350ºF. Cut squash in half lengthwise and scoop out seeds. Place squash cut side up in a large baking dish, drizzle with olive oil and season with 1/4 tsp. each salt and pepper. Cover dish with foil. Bake for 45 to 60 minutes or until flesh is tender when pierced with a knife. Set aside to cool slightly, about 10 minutes.
Make gremolata: Slice lemon zest lengthwise into thin matchsticks, then chop. Add zest to a bowl with parsley, garlic and 1/4 tsp. each salt and pepper.
Using a fork, scrape flesh from squash in long strands. Season with salt and pepper. (You should have about 3 1/2 cups.) Divide squash among 4 bowls; top each with 1/4 cup ricotta and about 1 Tbsp. gremolata. Drizzle with additional olive oil, if desired.