In medium saucepan, add peas and water. Bring to boil over high heat; reduce heat and simmer, covered, about 30 minutes or until peas are just tender. Drain any remaining liquid and transfer peas to a large bowl.
Coat large nonstick skillet with cooking spray; sauté onion, pepper and squash over medium to high heat, stirring occasionally, 5 minutes. Reduce to low heat, cover and cook 5 to 7 minutes or until squash is just tender. Stir in walnuts.
Add walnut mixture, vinegar and parsley to peas; stir to combine. Season with salt and pepper. Let cool slightly.
Spoon 1/4 cup of the mixture into each lettuce leaf. Fold the leaves in half over the filling and roll.
Makes: 4