The abuse occurred in various places in the county during babysitting sessions, and involved him drugging the children with sedatives so that they slept through the abuse, according to testimony on the first day of trial.
McOwen pleaded guilty Tuesday to one count of rape, three counts of indecent assault, and multiple counts of creating and distributing child pornography that depicted the abuse.
Judge William R. Carpenter accepted the plea agreement and immediately sentenced McOwen to 50½ to 101 years in state prison.
"Justice was absolutely done in this case," said Assistant District Attorney Samantha Cauffman. "May Barry McOwen never see the light of day again.
"He needs to be removed from society for the rest of his life, which is what a sentence of 50 and a half to 101 years promises to do."
Relatives of the girls cried with relief in the courtroom when they learned of the guilty plea.
"They have been through more than any family should ever have to go through," Cauffman said.
George S. Yacoubian Jr., McOwen's attorney, could not immediately be reached for comment on his cellphone.
Contact Bonnie L. Cook at 610-313-8232 or firstname.lastname@example.org. Read her blog MontCo Memo on philly.com.