Hi Kare:-) Okay. I have never made this salad for the number of people you need to serve but it is simple and tastes good, and, I think would be yummy with spaghetti. Here is my best guess for 50 people:

ROMAINE, CUCUMBER, TOMATO AND BASIL SALAD

10 to 12 packages of 3 romaine hearts, cores removed, then sliced, horizontally or crosswise into 1-inch pieces
10 to 12 English cucumbers, peeled, halved, and sliced
4 or 5 pint baskets of grape or cherry tomatoes, rinsed and halved
3 green peppers, rinsed, seeded, deveined, and slivered
1 to 1 1/4 cups fresh basil cut into chiffonade (leaves rolled and very thinly sliced)
Ken's Parmesan Peppercorn salad dressing

Put all ingredients, except dressing, in large salad bowl(s).

Serve bottles of dressing on the side so that each person can serve themselves.