1. Roughly chop tomatoes. Mix them in a bowl with the olives, avocado, shallot, most of oregano, few small splashes of vinegar, a glug of oil, salt, and pepper. Set aside for 5 minutes.
2. Tear larger lettuce leaves into pieces and leave the smaller leaves whole. Add them to the bowl, then dress everything with some of the lemon oil dressing. Move the dressed salad to a large plate or platter, leaving the wedges of avocado in the bowl. Place these around the outside of the plate. Crumble large chunks of feta all over the salad. Drizzle the salad one more time with oil and the rest of the oregano.