In a large skillet, heat the oil over medium-high heat. Add the bell pepper, jalapeno, onion and a pinch of salt and cook until softened, 7 to 10 minutes. Add the taco seasoning and cook for another minute. Add the ground beef and cook, breaking it up with a spoon or spatula, until browned, 8 to 10 minutes. Stir in the beans, corn and mild salsa. Transfer to a casserole dish and cover with the corn chips.
Bake until the casserole is heated through and the corn chips are lightly toasted, about 20 minutes. Top with the queso fresco, cilantro, radishes and a squeeze of lime. Serve with salsa verde.