In a mostly civil debate to be aired Wednesday night on television station WHYY, O'Donnell said unsustainable federal spending and a heavy tax burden were the main causes of the downturn.
The Republican said she would fight to shrink government and cut taxes, including extending all of the tax cuts passed under former President George W. Bush that are set to expire at the end of the year.
"We need to get out of the way of the small business owner, get out of the way of the entrepreneur and let them create jobs," she said.
Democrat Coons suggested a more aggressive federal role is needed, saying a lack of regulation helped spark the recession by failing to detect widespread problems in the housing and financial sectors that exploded into an economy-wide crisis.
"I think it was a lack of appropriate regulation," Coons said. "It's not reckless spending."
Coons said he supports extending most of the Bush-era tax cuts but repeated his concern about continuing income tax breaks for the wealthy.
"Each tax cut decision adds to the deficit, adds to the debt, and I think we need to choose responsibly," said Coons, the New Castle County executive.
He didn't say specifically the income level where he thinks the cuts should be allowed to expire.
He suggested several federal initiatives that he said could help the private sector, including providing subsidies for alternative energy, improving trade policy and investing in education to boost competitiveness.
Coons said he supports the Obama administration's "Race to the Top" education program that allows states to compete for federal grants by submitting innovative reform proposals. The program awarded Delaware $100 million earlier this year.
O'Donnell said she opposes the program, saying Washington is throwing money at failing schools without fixing the system first.
The two also disagreed on wind power development off the state's shore, with O'Donnell saying she opposes it for environmental reasons and Coons saying he supports it as a way to create jobs. They both said they would oppose oil drilling off the coast.
Coons and O'Donnell largely avoided the issue of religion and the Constitution that created a stir at a Tuesday debate, when O'Donnell questioned whether the Constitution provides for the separation of church and state. At an afternoon chamber of commerce forum in Rehoboth Beach, Coons briefly mentioned the controversy by saying he would fight to maintain the separation.
Coons and O'Donnell are vying for the Senate seat that was long held by Vice President Joe Biden and is now occupied by a former Biden aide, Democrat Ted Kauffman.