Masnada takes Tour of Oman lead
Quick-Step's Italian rider forged clear on the final descent to cross the line in Muscat over a minute clear of the chasing group.
Masnada, whose last stage win dates back to the 2019 Giro d'Italia, has a 1min07sec lead over teammate Mauro Schmid and six others going into Monday's penultimate fifth stage.
The 150.5 kilometre ride from Samail ends with a 5.7km climb up to the summit finish on Jabal Al Akhdhar.