The GWR▸ (the original one) had a programme to do this in the 1930's. The sections from Didcot to Milton, Wantage to Challow and from Shrivenham to Bourton were quadrified (to borrow a term from FTN) then.
Before lawyers assemble outside my tent, I will say that I originally borrowed the term, May probably be from bignosemac or Red Squirrel. But whoever called it whatever, I am all in favour of four-tracking.