Top-performing U.S. restaurant chains Panera Bread Co
, Chipotle Mexican Grill Inc and BJ's Restaurants Inc served up strong fourth-quarter results on Thursday.

Investors wanted to see signs of continued strength in sales at established restaurants -- a benchmark for restaurant performance -- and got just that from Chipotle and Panera.

Shares in these restaurants have risen sharply this year on industry-leading gains in sales, and investors have wondered how long their outperformance could last.

Chipotle, which features organic and natural ingredients, said fourth-quarter sales at established restaurants jumped 12.6 percent, an acceleration from the 11.4 percent climb in the prior quarter.

Shares in the popular burrito chain, which also reported quarterly profit that topped Wall Street's view, rose 6.9 percent to $274.44 after it repeated its forecast of a low-single-digit percentage gain in 2011 same-store sales.

Chipotle's stock has chalked up a 12-month gain of almost 160 percent.

Panera's shares have risen 38 percent in the last 12 months. Panera, which serves lavish sandwiches, salads and pastries, said same-store sales at company-owned bakery-cafes rose 5.2 percent in the fourth quarter.

The company on Thursday reported fourth-quarter profit that beat analysts' average view, boosted its full-year earnings forecast and called for 2011 same-store sales growth of 4 to 6 percent. Its shares jumped 10.6 percent.

BJ's Restaurants Inc , a restaurant and brewery, said sales at established restaurants were up 5.9 percent. It reported a gain of 6.7 percent for the third quarter.

But BJ's fourth-quarter profit just matched analysts' view, and shares in BJ's, which have gained about 85 percent over the last year, fell 4 percent to $37.09 in extended trading.

(Reporting by Lisa Baertlein and Renju Jose in Bangalore; Editing by Gary Hill)