The company plans to increase free-range production from 45,000 to 90,000 birds a week and organic production from 5,000 birds weekly to 20,000.
The company, in line with other chicken producers, has noticed a significant change in consumer demand following TV programmes by celebrity chefs Jamie Oliver and Hugh Fearnley-Whittingstall.
Speaking following a conference on organic poultry production in Edinburgh, Grampian spokesman Alasdair Cox said the impact of the two chefs' campaign had been significant, feeding through to an increase in demand for free-range and organic birds by customers at Tesco, Asda, Morrisons, Sainsbury's and Marks & Spencer.
Cox said: "Free-range has seen the bigger increase because organic is more expensive. The expansion is focused on free-range because that is where the most demand is. Organic is also more expensive to get into, both in terms of capital costs for setting up and ongoing costs. There is also a shortage of organic land and supply of chicken feed.
"Free-range and organic still represent just a fraction of our overall business, although both sectors are growing.
"Conventional chicken still accounts for 94% of Grampian's sales."