Greek Edamame Salad with Lemon Tofu Dressing

2 large cucumbers, peeled and chopped
2 tomatoes, seeded and chopped
1 1⁄2 cups torn iceberg lettuce
1 1⁄2 cups torn romaine lettuce
1 red onion, thinly sliced
1 cup edamame (whole green soybeans), shelled and cooked
1⁄3 cup ripe olives, pitted, sliced, and drained
12 oz. silken tofu
2 tbsp. soybean oil
1 tbsp. lemon juice
1 tsp. minced garlic
1⁄2 tsp. dried oregano
1⁄2 tsp. ground pepper
1⁄4 tsp. salt
1⁄2 cup crumbled feta cheese