Ouali began his career in the junior ranks of amateur club SCO Roubaix 59 in his native Roubaix. At age 15, his math teacher at the time recommended that he try out for Mouscron's academy, Futurosport, which was a short distance away across the Belgian border. Ouali took his advice and was admitted into the club shortly after.
Ouali progressed through the junior ranks of Mouscron, and on 27 January 2007, he made his professional debut for the club in a league game against KAA Gent. On 8 March 2008, Ouali started his first league game for the club against Brugge, scoring a goal in the 2–0 win. The following week, he started and scored again, this time against Charleroi. After scoring two goals in his first 2 starts for Mouscron, he was signed on 16 March 2008 to a two-year contract extension until 2010. On 14 September 2008, Ouali scored a hat-trick in a league game against Kortrijk. On 22 December 2008, it was reported that Ouali was joining Standard Liège for a fee of €400,000. However, the transfer did not go through because of Mouscron's refusal to sell after the news of the transfer was leaked to the press before its completion. On 28 December 2009, Mouscron were kicked out of the Belgian First Division and relegated to the Third Division after facing financial difficulties and going into administration. All the first team players of the club became free agents and were free to sign with other clubs. On 1 January 2010, Ouali went on trial with Ligue 1 side FC Sochaux. However, on 7 January 2010, it was reported that Ouali was close to signing with another Ligue 1 side, Le Mans.
Le Mans
On 8 January 2010, Ouali signed a two-and-a-half-year contract with Le Mans FC.
On 24 July 2012, Ouali signed a two-year contract with Dynamo Dresden. Despite the club's on-field struggles, finishing 16th and 17th in Ouali's two years at the club, he enjoyed a successful spell and reached good form. His pace caused problems for opposition defences as he established himself as an important first-team player.
Following Dynamo Dresden's relegation from the 2. Bundesliga in the 2013–14 season, Ouali signed a three-year contract with SC Paderborn 07, and represented them in the Bundesliga for the 2014–15 season. Paderborn were relegated to the 2. Bundesliga for the 2015–16 season.
Kortrijk
On 15 June 2016, Ouali joined Belgian club Kortrijk.
Hatayspor
On 5 August 2019, Ouali signed a contract with Turkish club Hatayspor.
