Congratulations to your son! I'm assuming this will be a mix of ages with family, his friends, etc.? Will it be an indoor event or more like a barbeque? The site below is a great help with recipes & quantities for large groups. A lot of them are make-ahead, as well.

Here is a link that might be useful: Growlies for Groups

Bebet,
I have gone through 2 high school graduations and my first recommendation is to find a friend that can come over about 15 minutes before your guests arrive (assuming your party is after the ceremony) and to put out your cold foods, stir the hots,etc. I did bbq beef or pork sandwiches in crock pots and they were a hit. Relish tray, fresh fruit, bakery cake, bowls of peanuts mixed with m & m's and an assortment of bars. In our instance, many people were going to several graduations, and just wanted to nibble on one thing. I also did punch and pitchers of ice water and iced tea. I also had my graduate select the foods they liked and also that our family liked so that if we were eating leftovers it was something that was going to keep. I avoided all mayo type salads for that reason. Also we made the sandwiches on the junior size buns. I set up my display with pictures, awards, etc. in one room and the food in the kitchen. I set up the garage with tables. If you are going to do a bakery cake; take your pictures with it and cut it right away otherwise it won't get eaten. Have fun and enjoy the day without stress. Keep us posted. Deanna

What I would recommend would depend on what time of day, if you would be doing it immediatly after the ceremony or at a different time and if you wanted a full meal or just open house snack sort of thing.
I do the funeral lunches for our church so I am familiar with planning food for a large group several times a year.
Linda C

I agree it really depends on the time of day, will this be an afternoon or evening event? Are you thinking a full meal? Inside or out?

I also get the feeling from your post this is not a High School graduation but perhaps a graduation from University, so a bit of an older than high school but younger than me crowed!!!

Let us know and I'm sure the ideas will flow and congrats to your son and to the parents that got him there!

depending on the ages of company..say most are your sons friends in the 18-22 yr old group Id go with a theme like Tex Mex...or BBQ...or Italian...or just a large buffet of pickin food like wings potato skins nacho platter etc! If you get a theme then I know all the good folks here can definately expand it with many good recipes!

I did a graduation party that worked out well that was Mexican food. I was able to make a couple trays of enchilatas both with red sauce and with a white sauce. I was able to freeze them ahead. I cut up lots of stuff for tacos and had a crock pot with a bean cheese dip and chips. I had a salad too. It was four years ago but I know it was a hit.