Karen's Spinach Salad

1/2 to 1 bag of baby spinach (washed, stems removed)
1 head iceberg lettuce or romaine
1 med purple onion, chopped
1 1/2 C. shredded Swiss cheese
6 fresh sliced mushrooms
1/2 pkg bacon, cooked & crumbled
mix together and add dressing

dressing:
3/4 C. rice vinegar (or white)
1/2 C. veg. Oil
1/2 C. sugar
1/2 T. dried onion flakes
1/2 t. salt
3/4 t. dried mustard
1/2 T. poppy seeds
combine, shake, chill
Add just before serving