Is this the main dish? Or a side to other dishes?
If it's a side, I would estimate a cup of rice to feed 5 people, and 1/4 cup of chopped onion and 2 T chopped green onion per cup of rice, and a can of tomato paste per every 4 cups of rice. Approximatly! When you cook in those quantities 1/2 cup of onion more or less makes no difference at all.
So for 70 I would estimate 14 cups of rice...but make it 15 just because that's a nice even number. There are 2 1/2 cups of rice per pound, so figure 7 pounds of rice to serve 70...but add another pound. Use 8 pounds of rice. I would plan on cooking it in 2 big stock pots for ease of stirring.
Chop onions enough to make about 4 cups chopped...likely 5 pounds would come close enough....and 4 green peppers. Divide between the 2 pots and sautee each batch in about 3/4 cup of vegetable oil. Add a T. of chopped garlic to each pot.
When soft....add 4 pounds of rice to each pot, stir to coat with oil, and add 4 quarts of liquid. I would use a food service can of chopped tomatoes for each pot. Measure the liquid and consider that that part of the 4 quarts...I would add 2 of those quart boxes of chicken broth to each pot and make up the rest in water....then toss in the chopped tomatoes. and add 1 1/2 cans of tomato paste to each pot....that's 3 cans over all....then season to taste....you will need more salt...but remember the broth is salty so start with a tablespoon in each pot....and about 2 teaspoons of ground cumin in eash pot....and I would add about 1 T of a hot pepper sauce like tobasco to each opt.
Add the spices before the rice is cooked so they mix well with the liquid. Cook slowly, stirring often uneil the rice is tender. Depending on your rice, you may have to add more water.....or you could use tomato juice. Then I like chopped cilantro added just before serving.
This should provide you with about 75 sligltly more than 1/2 cup servings.
Linda C

Wow that sounds good and those are very good directions Thank You Linda C.

Those are roughly the same ingredients that i use for my Spanish rice. It is the most requested dish i make for family gatherings, etc. I boil a whole chicken and sometimes add some of the chicken as well. It's all the rage. The chicken both is the key!

Thanks so much! Just the info I needed. Preparing this as a side dish for 70 folks.Thanks again!