Heading into the end of 2019, it's becoming increasingly difficult to find companies to add to a portfolio as 2020 is looking to be full of strong political headwinds and continued trade tensions. Despite these difficulties, it is possible to find worthy investments that can weather the potential big issues coming in the next year and enrich your portfolio while doing it. For instance, here are three restaurant stocks with confident 2020 forecasts -- including revenue, net income, and earnings-per-share growth -- to consider buying and holding for the long-term. 

1. Dunkin' Brands Group

The introduction of the Mobile On-the-Go platform in addition to premium espresso drinks and breakfast sandwiches is having a positive effect on Dunkin' Brands (NASDAQ:DNKN).

Dunkin' Brands opened 78 new locations during the recent quarter, totaling more than 13,000 Dunkin' and 8,100 Baskin Robbins locations. Comparable sales growth was 1.5%, which is expected to improve with upcoming remodels to each location. Dunkin' is remodeling 500 stores in 2019 -- upgrading the appearance and increasing the output of high-profit-margin items such as cold-brew drinks and baked goods.

Operating margins are improving each quarter, reporting 32.7% during the third quarter, 1.4 percentage points above the 2018 margin of 31.3%. Raising full-year 2019 guidance, earnings per share is expected to land between $3.10 and $3.12, an increase over the original estimate of $3.02 to $3.05.

Group of happy friends drinking coffee.

Image source: Getty Images.

Looking into the future, Dunkin' is midway through a three-year strategic plan announced back in February 2018. The Blueprint for Growth involves a drive to increase revenue to low- to mid-single-digit percentages and operating income by mid- to high-single-digit percentages by expanding the Dunkin' reach by 1,000 additional locations. Management stated in the plan to "eventually have a total of 18,000 Dunkin' locations in the United States."

CEO David Hoffman stated during the third-quarter conference call that "the U.S. Blueprint for Growth is working and the strategic investments made into the Dunkin' business last year are enabling us to drive top-line results and deliver a better guest experience."

As Dunkin' revamps locations to become more profitable through product additions like espresso drinks, breakfast sandwiches, and cold brew, its expansion  -- in addition to its 1.96% forward dividend yield -- is attractive for investors.

2. Chipotle Mexican Grill

Share prices of Chipotle Mexican Grill (NYSE:CMG) have been on a tear in 2019, up 74% so far, and they are up 96% from the 52-week low of $383 per share. Even after this massive 2019 run, Chipotle is still a buy.

The fast-casual restaurant chain took some time to recover from food safety problems it had in 2015. In early 2018, the former CEO of Taco Bell, Brian Niccol, came onboard as the new CEO and revamped the loyalty program, introduced drive-up windows, and expanded the menu. These additions have shown impressive results.

The recent third-quarter earnings report showed year-over-year revenue growth of 14.6% and an 11% growth in comparable-store sales. The most impressive result from the quarter was from digital sales, which grew 87.9%, accounting for 18.3% of revenue in the third quarter.

Chipotle opened 25 new restaurants during the quarter, totaling 2,546 locations. Chipotle expects to open a total of 140-155 new restaurants by the end of this year and between 150 and 165 new restaurants in 2020.

Shares of Chipotle are priced for performance, with a price-to-earnings ratio of 55.37, well above the sector median of 17 times. However, the price-to-sales ratio is showing a discount at 4.35 -- 2.72 points below McDonald's (NYSE:MCD) price-to-sales ratio of 7.07.

Giving back to shareholders, Chipotle repurchased $40.1 million in shares during the third quarter and $207.4 million in the trailing 12 months. Considering that digital sales reached $257 million in the third quarter, growing nearly 88% year over year, there are plenty of opportunities left for Chipotle to grow, increasing convenience and enabling customers to grab food on the go. Even at the current valuation, Chipotle is a buy.

3. Starbucks

Global coffee titan Starbucks (NASDAQ:SBUX) showed revenue of $24.4 billion in fiscal 2019 while operating 31,256 stores -- opening 630 new stores in 2019. Global comparable-store sales were up 5% overall -- 6% in the U.S. and Americas and 5% throughout China. The membership loyalty program has shown impressive results, increasing 15% year over year, totaling 17.6 million members.

Looking forward, fiscal 2020 guidance projections are between 3% and 4% in comparable-store sales growth. New store openings are projected to total 2,000 globally in 2020 -- 600 in the Americas and 1,400 elsewhere -- with expected "mid-teen" growth in China comparable store sales growth. Revenue is expected to increase between 6% and 8%, with an operating income improvement between 8% and 10%. Voicing assurance about the plans, CEO Kevin Johnson stated in the recent quarterly conference call that "strong performance throughout fiscal 2019 gives us confidence in a robust operating outlook for fiscal 2020."

With a forward price-to-earnings ratio of 26.84 and a price-to-sales ratio of 3.80, Starbucks is comparable to McDonald's price-to-earnings of 24.66. However, Starbucks is showing value against McDonald's price-to-sales ratio of 7.07. Giving back to shareholders, Starbucks returned $12.09 billion in fiscal 2019 -- $10.33 billion in share repurchases and $1.76 billion in dividends.

Starbucks has invested in technology, new locations, and product diversity, which has created a wide and deep moat around the company -- making Starbucks a no-brainer to buy and hold for the long term.