The move comes after both stocks sat on the sidelines for much of an epic bull market. From the start of 2012 to the third quarter of 2015, McDonald's shares fell 4 percent, and Coke shares rose 12 percent. This as the enjoyed a 56 percent rally.
Now that has been flipped on its head. Since September, with the S&P 500 up 5 percent, Coke has added almost 20 percent, and McDonald's is 34 percent higher.
The fast food giant has benefited from a turnaround effort that appears robust, with sales growing more than expected, as its launch of all-day breakfast appears to be a hit.
For its part, Coca-Cola has focused on margins amid stagnant global soda sales, attempting to cut costs and embarking on a major refranchising effort.
But even as the fundamentals have improved for both companies, the real driver for the stocks come down to risk appetites rather than human ones.
"This is a great lesson for traders, because what we're seeing is these stocks are going up not really because of what the companies do, but rather, there's been a sea change on Wall Street as far as these low-volatility, low-beta names," Eddy Elfenbein said Monday on CNBC's "Power Lunch."
Elfenbein, the editor of the Crossing Wall Street blog, is referring to the fact that both stocks have an unusually low correlation to the S&P, compared to most stocks within the index. On top of that, both pay above-market dividends, and are considered safe and stable stocks for potentially risky times.
Because he sees the twin moves as motivated more by a flip in sentiment than by an attractive value or growth proposition, Elfenbein says he would be disinclined from investing in either name.
"When you strip [their defensive qualities] away, basically you have two companies that are overvalued, are low-growth, and really extended. I'd stay away from both names," he said.
Turning to the charts, Todd Gordon of TradingAnalysis.com says that McDonald's shares could be an attractive short-term purchase at slightly lower levels.
"You can't buy the chart at all-time highs, but on a pullback, it's attractive," Gordon said Monday on "Power Lunch."
(Neither Elfenbein nor Gordon has a position in either stock.)