In a saucepan bring water to a boil. Add rice and stir. Reduce heat, cover and simmer for 20 minutes. Drain and set aside.

Simmer broccoli and cauliflower florets in water for 10 minutes, or until crunchy. Meanwhile, preheat oven to 350 degrees F (175 degrees C).

In a large saucepan, melt butter and saute onion. Stir cauliflower, broccoli and rice into the saucepan. Once the vegetables and rice are coated, stir in the cheese, chicken soup and milk. Transfer the entire mixture to a 9x13 inch baking dish and sprinkle the crackers on top.

Bake in a preheated 350 degrees F (175 degrees C) oven for 30 minutes.