Shrimp Ceviche Cocktail recipes

Name: Shrimp Ceviche Cocktail recipes
Ingredients: 1/4 cup chopped red onion; 2 small limes, squeezed; 1 tsp olive oil; 1 lb large cooked shrimp, peeled and deveined*; 1 medium hass avocado, diced into chunks; 1 medium tomato, diced; 1 cup diced English cucumber, not peeled; 1 serrano pepper, seeds removed and minced; 2 tbsp chopped cilantro, plus more for garnish; salt; black pepper; 1 lime cut into wedges for serving; 2 1/4 cups shredded iceberg lettuce