Ouahab, ranked No. 752, needed just 60 minutes to dispatch sixth-seeded Robin Haase 6-3, 6-2. Ouahab dropped just 16 points over his nine service games and faced two break points.
He won nearly half the points off Haase's serve and converted all four of his break chances in picking up his first ATP main draw victory since 2007.
Seventh-seeded Albert Ramos easily got past Pere Riba 6-2, 6-3 behind five service breaks. Ramos was good on 61 percent of his first serves and won 84 percent of the points in those situations.
Qualifier Sergio Gutierrez roared past Rui Machado 6-2, 6-1, winning 60 percent of the points off Machado's serve and finishing off five of his six break opportunities.
Matthias Bachinger edged past Filippo Volandri 6-3, 3-6, 6-3 and Flavio Cipolla topped Yassine Idmbarek 6-1, 2-6, 6-1 in the matches Tuesday that went three sets.