He had pleaded not guilty to her murder at the outset of his weeklong trial. A Victoria state Supreme Court jury found him guilty Saturday.
Boyle told the court he found 30-year-old Edwina dead in bed with two bullets in her head and one of his neckties around her throat.
He said he thought he would be a suspect because he was having an affair, so he hid her body.
"Obviously, I didn't want to be charged with a murder I didn't commit," he told the court.
The couple migrated from Wales in 1972.
Boyle had told his two daughters their mother ran off with a truck driver, but a son-in-law found Edwina's remains in the 45-gallon drum while tidying the yard in October 2006.
Boyle faces life imprisonment. A sentencing date has not been set.
