Spinach Salad

2 bunches spinach
1 head lettuce
1 purple onion
3/4 lb mushrooms, sliced
3/4 lb swiss cheese
½ lb bacon, cooked and crumbled

Dressing

3/4 tbsp poppy seed
1/3 cup vinegar
3/4 cup oil
1/3 cup sugar
3/4 tsp grated onion
3/4 tsp salt
1/3 tsp dry mustard