Wash and dry the lettuce; chop it into bite-sized pieces. Thinly slice the radishes. Zest the lemon.
If the peas are frozen, thaw them in some warm water. If the peas are fresh, boil some water, add the peas and cook for about 3 to 4 minutes, until tender and bright green, then remove them and rinse with cold water.
Finely chop 1 tablespoon oregano leaves. Make the Lemon Vinaigrette, then stir in the oregano.
To serve, place the lettuce leaves in serving bowls or plates. Top with sliced radishes, peas, crumbled feta cheese, and lemon zest. Drizzle with vinaigrette and top with fresh ground pepper.