Preheat oven to 375 degrees F. Cut squash in half lengthwise. You can remove the seeds before or after baking, but I find it’s easier to do after. Spray cut edges of squash with non-stick cooking spray, and sprinkle with salt and pepper. Lay cut side down in a 9×13 casserole dish and bake for 35-45 minutes. For easier cutting, use a fork to poke a few holes in a whole squash and microwave for about 4 minutes, then cut in half lengthwise and bake. Reduce baking time to 30-40 minutes. Remove from oven when the skin is easy to puncture with a fork.
While the squash is baking, begin cooking the bacon. Heat 2 tablespoons oil in a deep non-stick skillet over medium heat. Cook bacon until crisp and browned, stirring occasionally. This took about 10 minutes for me, but it will vary based on the kind of bacon. Remove from the pan and set aside.
Next, add remaining 1 tablespoon oil to the same pan. When hot, add ground meat and use a wooden spoon or spatula to break up into small pieces as it cooks. Add 1 teaspoon oregano and 1 teaspoon salt. Continue to cook until completely browned and cooked through. Remove from heat and let cool.
Meanwhile, when the squash is done baking, let it cool until it’s easy to handle. Next, run a fork through the flesh – long spaghetti-like strings should appear and easily separate from the squash. Scrape all the stringy flesh from the shells and add to a large mixing bowl (should be at least 3-4 cups of squash, roughly). Discard shells, but save the casserole dish.
Reserve about 2 tablespoons of bacon bits. To the large bowl with the squash, add remaining meats, pizza sauce, greek yogurt, 1 cup mozzarella cheese, egg, basil, remaining 1 teaspoon oregano, 1/2 teaspoon salt and 1/2 teaspoon fresh ground pepper. Mix thoroughly and then flatten the mixture into the casserole dish.
Top with remaining 1/2 cup cheese, whole pepperonis, and reserved bacon bits. Bake uncovered at 375 F for 22-25 minutes. For a crispy top, broil for the last 3 minutes.
Serve immediately or portion out as lunch leftovers. This casserole tastes even better the next day! Consume within 4 days.