You can take a train from Oxford to Nottingham via Birmingham New Street in around 2 h 44 min. Alternatively, National Express operates a bus from Oxford to Nottingham once daily. Tickets cost $15 - $20 and the journey takes 5 h 10 min.
From Oxford train to Birmingham New Street then train to Nottingham. 2 h 44 min £84. From Oxford bus to NOTTINGHAM, Station Street. 5 h 10 min £14. From Gloucester Green Bus Station bus to Buckingham, High Street (The Grand Junction PH), bus to Milton Keynes Coachway, then bus to NOTTINGHAM, Station Street. 5 h 12 min £23. From Oxford drive to Nottingham. 1 h 48 min £19.