Because this new policy takes up crucial drive-thru seconds, McDonald's has to find a new way to preserve speed. The chain's answer? It plans to discourage "suggestive selling," an industry term for trying to make customers spend more money on food and drinks by proposing buying additional items, according to a document obtained by CNBC.
Read MoreDining at McDonald's is about to change
Crew are also urged to keep food bags open so customers can easily check whether drive-thru orders are correct. While some restaurants CNBC called are already using the new process, McComb said all restaurants will implement it "later in the summer."
"At McDonald's we're always looking for ways to improve the customer experience. Ask, Ask, Tell is a program we're implementing nationwide to help improve that experience in our drive-thrus," McDonald's spokeswoman Lisa McComb told CNBC on Friday.
McDonald's U.S. generates more than 60 percent of sales at the drive-thru.
Read MoreWill McDonald's mix-and-match strategy work?
In July 2013, then-CFO Peter Bensen told analysts the chain was "employing more suggestive selling strategies at the order point to encourage trials of new products and add-on purchases."