Preheat oven to 400 degrees Fahrenheit.
Cut the top and bottom off of each spaghetti squash, then stand on one end and slice through the squash carefully.
Scoop out seeds and stringy bits.
Rub with olive oil, salt, and pepper.
Place cut-side down on a parchment paper-lined baking sheet.
Bake for 40-60 minutes, depending on squash size and oven strength.
Once you can pierce the squash with a fork easily, shred and 'fluff' the squash with a fork until you get strings of 'spaghetti'. Keep the squash noodles inside its boat.
Add a drizzle of olive oil into the squash noodles, and about half of the mozzarella cheese. Mix well.
Add other toppings, and the rest of the cheese. Place back in the oven for 5-8 minutes, broiling at the end if desired, until cheese is melted