In a large skillet cook beef and onion. Drain. Stir in tomato sauce and taco seasoning. Bring to a boil. Reduce heat and simmer uncovered for 5 minutes.
Separate crescent dough into 8 triangles. Place in a greased 9 inch pie plate with points toward the center. Press onto bottom and up the sides for a crust. Seal perforations. Sprinkle 1 cup of chips over crust. Top with meat mixture.
Carefully spread sour cream over meat mixture. Sprinkle with cheese and remaining chips. Bake at 350º 20-25 minutes or until cheese is melted and crust is golden brown. let stand for 5 minutes.