The S&P 500 rose 1.05% to 1,703.46 in midday trading Thursday.
The Dow Jones industrial average was up 0.71% to 15,609.95, while the Nasdaq was up 1.03% to 3,663.57.
The yield on a 10-year Treasury bond rose 3.97% to 2.70%.
The price of gold slipped 0.11% to $1,311.50 per ounce.
Shares of Huntington Beach-based restaurant operator BJ's Restaurants Inc. were down about 11% to $31.87 on disappointing results for the quarter ended July 2. Roth Capital lowered its rating on the company's stock from "buy" to "neutral." BJ’s had a recent market value of $897.52 million.
Irvine-based Masimo Corp. was up about 7% to $24.94, a day after beating consensus estimates on its second-quarter earnings. Masimo had a recent market value of $1.41 billion.
Anaheim drug maker Questcor Pharmaceuticals Inc. shares continued to climb, up about 4% to $69.57 for a market value of $4.02 billion. Questcor's shares closed up about 10% on Wednesday after reporting second-quarter results earlier this week that were driven by strong sales of its sole drug Acthar.
Irvine-based laser maker Newport Corp. reported second-quarter results in line with analyst estimates on Wednesday. Investors sent the company's share up about 6% to $15.48 on Thursday for a market value of $604.96 million.
Aliso Viejo-based Smith Micro Software Inc. shares were off about 10% to $1.03 for a market value of $38.38 million. The company reported second-quarter results on Wednesday that missed analyst expectations on earnings and the company also announced plans to shutter offices and lay off workers.