"Restaurants have been a very strong sector year-to-date, with the top half of stocks under our coverage outperforming the S&P on total return by 11 percent to 40 percent," JPMorgan analysts wrote in a note.
They point out that much of the price performance has been driven by multiple expansion and not an increase in earnings forecasts, which means investors should become more selective as sales soften.
Casual dining chains in particular look vulnerable to softening sales after their run-up. JPMorgan downgraded Brinker, Texas Roadhouse and Bloomin' Brands, saying the group now looks fairly valued with modest same-store sales declines likely.
Baird, meanwhile, cut Buffalo Wild Wings to neutral from buy, after the stock surged 36 percent year to date.
"The increasingly positive sentiment on Buffalo Wild Wings likely has been fueled by expectations for strong earnings growth to emerge in the second half of 2013/2014 behind solid top-line momentum and margin leverage [amid lower year-over-year wing costs]," the Baird analysts wrote, but added that the positives are being factored into the shares at current levels.
While JPMorgan analysts are more cautious on the casual dining chains, they continue to maintain overweight recommendations on McDonald's, Yum Brands and Starbucks. Starbucks was the top pick of the three; the analysts are now indifferent but wrote the stocks "should ideally be bought lower."
(Read more: Starbucks CEO: We're in early stages of growth)