2/3 c. oil
1/3 c. wine vinegar
1 tbsp. horseradish
1 tbsp. grated onion
1 tsp. salt
1 tsp. dry mustard
2 c. cooked roast beef, sliced on diagonal
1/4 tsp. pepper
1 head Romaine lettuce
1 head Iceberg lettuce
Cherry tomatoes
Sliced onions
Sliced mushrooms

Blend oil, vinegar, horseradish, onion, salt, mustard, and pepper. Refrigerate. Toss greens in large bowl. Arrange beef, tomatoes, mushrooms, and onions on top. Toss with dressing.