Step 1Spray bottom of large saucepan with nonstick cooking spray. Heat oil over medium-low heat, then add shallot and saute about 1 minute, stirring. Stir in orzo. Add broth. Heat to boiling. Reduce heat, cover and simmer until orzo is tender and liquid is absorbed, 10 to 11 minutes. Put orzo in large bowl. Stir in vinegar and lemon juice. Stir in tomatoes, zucchini, yellow squash, green pepper, onion, basil, salt and pepper.
Step 2Cover and chill 1 hour. Stir in lettuce. Spoon into serving bowl and sprinkle with sunflower seeds.