Cat eating grass, vomiting

Question
We allow our two 12-year old cats to spend pleasant, warm days in our fenced-in back yard. One cat has a fine time, but the other has taken to eating grass and later vomiting the contents inside the house.
Is there a way to discourage this cat from eating grass? Or, because of his age, is it a symptom of a larger problem? Unfortunately, if we keep the grass-eater indoors all the time, he would make an awful fuss if we let the other cat go outside.

Answer
when a cat is suffering from indigestion or nausea, it eats grass to empty its stomach or to serve as a laxative.  If the cat does this repeatedly it should be examined to find out the cause.  Your cat may have gastritis which is an inflammation of the stomach characterized by nausea and vomiting.  Sometimes overeating or eating the wrong foods will cause this condition.  Along with the grass eating, the cat is very thirty and demands water to soothe its inflamed stomach.  I could be wrong, I've seen my cat do this eat a whole bunch of grass and then spit it up like hes not able to get the grass down his throat, and i know he doesn't have gastritis,  most likely your cat is using it to help digest his food, if your really worried have your cat checked by a vet