Spinach Salad

2 bunches of spinach.  (prayed off and spun dry)
1 small iceberg lettuce
1 purple onion
1 cup mushrooms (sliced)
3/4 cup grated Swiss cheese
1 pound cooked bacon (crumbled)

Dressing:
3/4 teaspoon poppy seed
1/3 cup white vinegar
1/3 cup sugar
3/4 tablespoon grated onion
3/4 cup oil
3/4 teaspoon salt
1/3 teaspoon mustard