Combine all dressing ingredients in a processor until well combined; set half of the dressing aside and refrigerate to serve at the table.
In a bowl combine the cooked shell pasta with the remaining half of the dressing, then mix in cucumber, olives, sliced onion, pimientos and 1/2 cup crumbled feta cheese; toss to combine, then refrigerate while grilling the steaks.
Grill the steaks until desired doneness; place on a plate allow to rest for 15 minutes or more, then slice thinly.
Line a large platter plate with lettuce leaves.
Spread the pasta mixture over the leaves, then arrange the sliced steak over the pasta.
Sprinkle about 1/4 cup or more crumbled feta cheese over the sliced steak.