Drain red and white kidney beans well; place beans in a large bowl.
Drizzle with vegetable oil and vinegar; sprinkle with parsley, sugar and dip mix; toss to mix well.
Cover; chill at least an hour to season and blend flavors.
(Or let stand at room temperature if you prefer salad not too chilled.)
When ready to serve, place shredded lettuce in a large casserole or bowl.
Sitr sour cream into bean mixture; spoon on top of lettuce; sprinkle with onion rings.