Dollar-denominated soybeans also rose, although fundamentals for soy, corn and wheat remained bearish due to downside pressure from a swift harvest in the United States and competition on export markets from Black Sea suppliers.
"We are seeing a strong session across all risk assets, including agricultural commodities, and it appears to be linked to the optimism that the markets have displayed following the European summit," said Luke Mathews, a commodity strategist at Commonwealth Bank of Australia.
"We continue to note the seasonal harvest progress in the United States, which remains ahead of normal. It is acting as a headwind to prices, but right now the market is focused on the European situation."
US farmers are content to withhold harvested grain and wait to see if prices rise before selling.
Chicago Board of Trade December corn rose 1.6 percent to $6.47-1/2 a bushel by 1202 GMT, and December wheat gained 2.22 percent to $6.33-3/4 a bushel. November soy was up 1.88 percent to $12.33-1/4 a bushel.
World stocks and the euro rose to their highest levels in nearly two months after European leaders struck a deal to resolve the two-year-old euro zone sovereign debt crisis, which threatens the survival of the common currency.
The dollar fell to a six-week low against the Swiss franc, losing 1 percent on the day as it came under selling pressure across the board as investors were encouraged to take on more risk.
On Wednesday, corn slid on news that Japan had bought a cargo from Ukraine, which is likely to harvest a record crop this year.
Ukraine may compete for more business with the United States, the world's biggest corn exporter. Japan is the top buyer of US corn.
Similarly, wheat came under pressure from news that Egypt, the world's largest wheat importer, bought 120,000 tonnes of Russian wheat at its latest tender.
No US wheat was offered at the tender, a signal that US grain cannot compete.
Australia, typically the world's fourth-largest wheat exporter, is set to reap an estimated 25.05 million tonne crop in 2011/12, following late September rain, National Australia Bank Ltd said, up from its August estimate of 21.9 million.
European wheat likewise rose on optimism over the sovereign debt deal, although the strong euro capped gains because it makes European exports less competitive.