McDonald's could report its best U.S. sales performance in almost four years on Monday, and much of it will be credited to menu changes.

Plan, test, feedback, tweak, repeat. For the world's largest burger chain in the midst of a comeback, every step is especially vital.

There was a time when McDonald's took years to introduce menu items. Now, under the leadership of CEO Steve Easterbrook, it's often just months. McDonald's launched all-day breakfast in October after only nine months of planning.

What makes a menu

A typical menu has about 120 to 140 items, including size variations, and about 100 of those are specific to a region. In greater Chicago, that includes McDonald’s newest addition, the customer-designed ChiTown Classic, the winner of the area's Burger Build Off contest.

McDonald's gives its U.S. franchisees a lot of leeway but requires them to carry 40 items: classics like the Quarter Pounder with Cheese, Filet-O-Fish and McChicken, but also a range of wraps, salads and new items like mozzarella sticks. Each of its 36,000 worldwide restaurants serves the Big Mac, cheeseburger, hamburger, chicken nuggets and fries.

The average wait time for a customer at McDonald's is about 90 seconds, so there's not a lot of wiggle room when it comes to allowing food with long prep times on the menu.

"As a cook I'd really like to focus on 20 items and do them really well than have 50 that we can only do OK," said Dan Coudreaut, McDonald's executive chef. "It's all about balance."

In the test kitchen

It can take months. Even years. The burger chain looks not only at what part of the menu they want to tweak but what customers they want to attract. Millennials, for example, tend to prefer snack-type items over big burgers.

Make a plan The team makes an action plan, brainstorms concepts and ranks them. Food science In the test kitchen at McDonald's Oak Brook headquarters, where some products are conceived, chefs, food scientists and nutritionists all weigh in. Focus groups The food is tested with a focus group and tweaked, accounting for everyone's input.

Internal testing

At McDonald’s Oak Brook headquarters where some products are conceived, chefs, food scientists and nutritionists all weigh in before the food is tested with a focus group and tweaked, accounting for everyone’s input. Then in a nondescript Romeoville warehouse where McDonald’s has its Innovation Center, workers spend four to five weeks learning how to prepare the new item quickly and accurately, in a simulated setting. Plastic chairs stand in for cars in a mock drive-through lane.

Operations Practice, practice, practice! After weeks testing how to make new products in a simulated environment (folding chairs standing in for car seats in a drive-thru setting), new products move on to being served in the real deal restaurants.

Restaurant testing

After being tweaked, tested and tested again, the food is ready for the big time ... kind of. McDonald's asks a group of franchisees to put the item on their menu for a short time. The company tests products in regions where that type of food is most popular. That means chicken items get tested in Atlanta, coffee in the Northeast, salads on the West Coast and burgers in Texas.

Food types tested by region The Midwest? We like "a little bit of everything," said Lance Richards, vice president of menu strategy. McDonald's is currently testing Monster Energy Drinks in Illinois, and macaroni and cheese in Ohio. Breakfast bowls are getting a spin in California, and sweet potato fries are trying out in Texas. ANALYTICS Sales figures and customer comments are analyzed. Some products undergo more testing, some head to more restaurants and some head back to the drawing board.

Regional roots

Some menu offerings that were thought to be just for one region go national.

Sweet tea was developed for restaurants in the South but is now sold nationwide. Ditto for mozzarella sticks, which were requested by New York franchisees and launched nationwide this month. McWraps, which began in Austria and Poland in 2004, were brought to the U.S. in 2013 after being "altered" to cater to American tastes.

What do you add to a wrap to make it more palatable for Americans? "Ranch dressing," Coudreaut said. "And bacon."

What's ahead

While McDonald's is largely mum on what new foods are being considered, Coudreaut and Richards said the company is taking a closer look at the menu's components than perhaps ever before.

In years past, Coudreaut said there were some core menu items that were considered off-limits for change. But now, everything is on the table. And food, not speed, is now the first priority. "We're having the tough conversations," Coudreaut said.

"Operational efficiency has actually moved down in the ranks of priority because we want to focus most of all on the food," Richards said. "There's an openness to really going after the consumer that's so refreshing. I think there's some bright days ahead."

sbomkamp@tribpub.com

Twitter @SamWillTravel

Tribune illustrations by Phil Geib