Hi, I can't find any information about Patrick Doyle, but I think you need to examine the 1860-1870 censuses for St. Clair County, IL (O'Fallon is in St. Clair County) for Lizzy's family. In 1860 there is a Morrissey family in Township 1, Range 9 of St Clair Co as follows:
Thos. Morrissey age 30 born Ireland Anneage 30 born Ireland Cathrineage 3born New Jersey Thomasage 1born Illinois
This family is still there in 1870: Th. Morrissey age 45born Ireland Annage 36born Ireland Katharinaage 14born Illinois Theodorage 10born Illinois Johnage 8born Illinois Johanneage 5born Illinois Maryage 3born Illinois
I haven't found this family in 1880, but I would guess they're still in the area if Catherine's daughter was born there in 1883. St Clair County is just across the Mississippi from the metro St. Louis area. Adams County is north of O'Fallon, but about a hundred miles away.
Given the proximity to St. Louis, you may need to check there for marriage data for Catherine "Lizzy" and Patrick Doyle. Good Luck!