Dice the onion and bell pepper, mince the garlic, shred the chicken, drain and rinse the beans, drain the corn, cut the tortillas into strips, and shred the cheese.
Heat oil in a 12-inch oven-safe skillet over medium heat. Cook the onion and bell pepper until softened, about 4-5 minutes. Add garlic and cook until fragrant, 30-60 seconds.
Add shredded chicken, taco seasoning, black beans, and corn to the skillet. Stir to combine, seasoning with salt and pepper, and cook for 1 minute.
Pour in both cans of enchilada sauce and stir to coat everything evenly. Bring to a gentle simmer and cook for 3-4 minutes to thicken slightly.
Fold in the tortilla strips, pressing them into the sauce until fully submerged. Cook for 3-5 minutes until they soften and absorb the sauce, covering the skillet for 2-3 minutes if desired.
Preheat the broiler to high. Top the skillet with ¾ cup of shredded cheese and broil for 3-5 minutes until melted, golden, and bubbly.
Rest the skillet for 2-3 minutes, then top with remaining cheese and desired toppings like sour cream, avocado, cilantro, jalapeños, and tomatoes. Serve directly from the skillet.