Preheat oven to 375 degrees. Lightly grease a baking sheet.
Carefully cut the squash in half. Drizzle a little oil on each half, then place flesh side down on the baking sheet. Bake for 40-45 minutes, until the squash are tender.
In a medium bowl, add black beans, corn, chili powder, cumin, salt, and pepper; stir to combine. Set aside. (You may want to warm this in the microwave before serving.)
In a skillet, warm about 1 tablespoon olive oil. Add the sliced peppers and season with salt and pepper. Sauté for about 7 minutes, until the peppers are tender and slightly browned.
When the squash are done, stuff with romaine, black bean mix, and peppers. Top with guacamole, salsa, cilantro, and any other desired toppings.