Preheat the oven to 375°F and fill a 9 x 13” glass baking dish with about an inch of water.
Wash the spaghetti squash and then slice off the stem at the top. Cut each squash in half lengthwise and then use a spoon to scrap out the seeds and the darker yellow strands that the seeds are attached to.
Place in dish cut side up, cover with foil, and roast in the oven for 30-45 minutes, depending on the size (longer for larger squash). You can test to see if it’s done by scraping the inside with a fork. Strands should come loose as you scrape all the way down to the flesh.
While the squash is roasting, prepare the filling by warming oil in a large pan over medium heat. Sauté the red onion for a few minutes and then add the peppers and jalapeno.
When the squash is done cooking, allow it to cool for a few minutes before handling.
Scrape about 3/4 of the inside out into a bowl; add beans, salsa, corn, onion mixture, & cilantro. Stir together & press mixture into squash shells; top with shredded cheese.
Cook 20 minutes more until the cheese is bubbly and golden brown then serve!