Morgan in 2007 was the author of assisted-living legislation that became law.
Morgan, an attorney, denied taking bribes. He said Crosby paid him $1,000 a month for a year for legal services.
He testified Crosby hired him to sue the Health Department. He said he later advised Crosby not to sue. He denied ever meeting Crosby at the Capitol.
Morgan was Senate president pro tem in 2005 and 2006. He was Senate co-president pro tem in 2007 and 2008. He left the Legislature at the end of 2008 because of term limits.
Crosby did not face any charges over the payments to Morgan.
Morgan, 57, of Stillwater, faces up to 10 years in prison on his bribery conviction. Morgan is seeking probation and still claims he is innocent. Sentencing is set for January.
Morgan's attorneys at trial claimed Crosby lied about what happened in an effort to get leniency in his own criminal case.
Crosby has had a series of health problems since he was charged in 2010 including a heart attack that year.
He suffered from blood clots in his lungs after hip replacement surgery this year.