As a part of a campaign to persuade people to eat more healthily, the fast food firms have pledged to cut salt and fat levels in the next year.
Staff will be trained to give diners information on healthy options and chefs will cook food without added sauces or salt.
One of the firms Nando's has promised to make nutritional details public.
Burger King has decided to cut the salt content in its burgers, while KFC will be introducing lower-fat mayonnaise.
McDonald's is launching new fruit and vegetable options for children.
The Food Standards Agency (FSA) will supervise the changes, which will affect more than three million British people a day.
"Eating out should be fun and we don't want to change that, but we believe restaurants can help make it easier for us to take healthier choices," the Daily Star quoted Rosemary Hignett, head of nutrition at the FSA as saying.
The FSA intends to announce similar agreements with coffee shop chains, pubs and small restaurants.