Preheat oven to 400 degrees F. Line a large baking sheet and coat with nonstick cooking spray.
Using a melon baller or metal spoon, hollow out centers of each zucchini. Place on prepared baking sheet. (If the zucchini halves don't sit level, cut a bit off the underside.)
Add oil to a large skillet over medium-low heat. Once hot, add onion, red pepper, and poblano or jalapeno. Cook for 4-5 minutes, until veggies have softened.
Add rice, corn, beans, salsa, chili powder, cumin and salt. Stir well. Continue to cook for about 5 minutes. Remove from heat and stir in cilantro; set aside.
Spoon rice mixture into each zucchini, filling to the top. Sprinkle with cheese.
Bake for 20-25 minutes, until zucchini is tender and cheese is melted.