Oudenaarde is easily reached from Ghent (30 minutes by train) and from Brussels (1 hour). Trains run from Ghent Sint-Pieters station with connections at Ronse or direct services on the Ghent–Kortrijk line. The station is about ten minutes' walk from the Markt.
By car, Oudenaarde sits on the E17 motorway between Ghent and Kortrijk, with a well-signed exit. From Brussels, the E40 toward Ghent then south on the E17 takes about an hour. Parking near the Markt is straightforward outside race weekends — on the first Sunday in April, the Tour of Flanders effectively closes the region's roads and parking is a serious challenge; arrive by train or very early.
From Ghent, the train is the obvious option. From Bruges or Brussels, Ghent is the natural interchange.