Cook beef and onion in a large skillet until meat is browned, stirring to crumble meat. Drain. Stir in beans and chili powder; cook, uncovered, until thoroughly heated. Remove from heat; stir in taco sauce and salad dressing. Cool slightly.
Combine lettuce and green onions; place in a large bowl. Crush chips, reserving several whole ones for a garnish. Place chips on each serving plate, layer the lettuce, meat mixture, avocado, tomatoes and sprinkle with cheese.
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