The roll-out of the sandwiches, due to be completed by the end of September, follows a successful trial in the North-East.
The range, which comprises seven variants, is already available in the US. The sandwiches are made to order on fresh brown or white subs, with fillings including chicken tikka, and mature cheddar and grilled veggie melt.
The latest addition to the menu follows a similar launch by Burger King, which introduced a premium baguette line last year.
The Toasted Deli Sandwich range is also intended to compete with Subway, which has enjoyed rapid growth in recent years and has more outlets than McDonald's in the US.