Lentil Salad

1 cup cooked lentils
1/4(one-quarter) cup olive oil
2 teaspoons cider vinegar
1/2 (one-half) cup each: chopped celery and green pepper
1/4 (one-quarter) cup each: chopped red pepper and purple onion
2 cups torn lettuce greens

Combine lentils, oil and vinegar in a salad bowl. Stir well. Add celery, green and red peppers and onion. Toss to coat vegetables. Cover and chill until ready to serve over lettuce greens. Garnish with tomato. Yields four servings.