The S&P 500 was up 0.8% at 3,423.19 during midday trading.
The Dow Jones Industrial Average rose 0.9% to 28,184.56.
The Nasdaq climbed 0.6% to 11,379.65.
The yield on a 10-year Treasury bond rose 1.4% to 0.649%.
The price of gold decreased 0.4% to $1,940.
The price for a barrel of oil rose 0.3% to $42.45.
Shares in Lake Forest-based Del Taco Restaurants Inc. (Nasdaq: TACO) rose 5.9% to $9.19 apiece for a market cap of $343 million. Earlier in the day, C.L. King & Associates initiated coverage by setting the rating at Buy.
Shares in Lake Forest-based medical device maker Staar Surgical Company (Nasdaq: STAA) fell 2.9% to $46.63 apiece for a market cap of $2.1 billion. Staar shares have fallen 24% since a 52-week high of $62.51 on Aug. 5 when a short trading firm, J Capital Research, accused the company of financial irregularities in reporting its revenue from China.
Shares in Irvine-based Pacific Premier Bancorp. Inc. (Nasdaq: PPBI) rose 5.9% to $22.62 apiece for a market cap of $2.1 billion, for an almost 7% share price increase over the last month.