Preheat oven to 350 degrees F (175 degrees C). Lightly oil a 9×13 inch baking dish.
Saute onion, green pepper, eggplant, and mushrooms in oil until soft. Mix in fajita seasoning.
Line prepared baking dish with flour tortillas. Mix flour and eggs and then beans and corn. Spread bean mixture over tortillas. Spread the onion mixture over the beans. Top with salsa and mozzarella cheese. (Optional: sprinkle with black olives.)
Bake uncovered until heated through, about 30 minutes.