Heat oil and cook onion, tomato and green pepper until onions and pepper are tender, about 5 minutes. Add shrimp and heat for 2 minutes, then remove mixture from heat. Transfer to large bowl. Add olives and 1/2 of the grated cheese to the shrimp mixture. Cover bottom of rectangular glass baking dish with Salsa Verde (see recipe). Heat tortillas in oil just until soft and limp. Place some of the shrimp mixture in the center of each tortilla, roll and lay seam-side down in the baking dish. Coat the surface of each enchilada with Salsa Verde. Bake 350 for 20 minutes. Serve topped with garnish of shredded lettuce, cheese, green onions, avocado and sour cream. (To substitute scallops instead of the shrimp, cook them slightly longer, but just until tender. Be sure to drain off any excess liquid before adding cheese and olives.)