THIS STUDY INVESTIGATES THE EFFECT OF OUTPUT PRACTICE TASKS ON THE ACQUISITION OF ENGLISH MODALS. THE ACQUISITION IS MEASURED IN TERMS OF EVALUATING THE COMPREHENSION AND PRODUCTION PROCEDURALIZED SKILLS. A PRETEST POSTTEST AND DELAYED POSTTEST DESIGN WAS USED WHERE THE PROCEDURAL KNOWLEDGE WAS SPECIFICALLY OPERATIONALIZED THROUGH THE GROUPS’ PERFORMANCE ON TIMED GJ AND COMPLETION TESTS. TWO INTACT CLASSES OF INTERMEDIATE EFL LEARNERS WERE RANDOMLY ASSIGNED TO TREATMENT AND CONTROL GROUPS. THE TREATMENT GROUP, HERE THE OUTPUT GROUP (N= 27) RECEIVED A) EXPLICIT GRAMMAR INSTRUCTION, B) A COMBINATION OF THREE OUTPUT TASKS INCLUDING DICTOGLOSS, INDIVIDUAL TEXT RECONSTRUCTION, AND CORRECTED-CLOSE TRANSLATION , AND C) FEEDBACK. THE CONTROL GROUP (N=25) WERE JUST EXPOSED TO THE IDENTICAL TEXTS TROUGH LISTENING AND READING TASKS FOLLOWED BY SOME QUESTIONS IRRELEVANT TO THE TARGET STRUCTURE. RESULTS SHOWED THAT ON THE POSTTEST, ADMINISTERED 10 DAYS AFTER THE LAST TREATMENT SESSION, THE OUTPUT GROUP OUTPERFORMED THE CONTROL GROUP IN BOTH MEASURES OF PROCEDURAL KNOWLEDGE. FORTY DAYS LATER, THE OUTPUT GROUP’S PERFORMANCE WAS STILL SIGNIFICANTLY BETTER THAN THAT ON THE PRETEST. THIS GROUP ALSO SUCCEEDED IN RETAINING ITS OUTPERFORMANCE ON BOTH MEASURES OF PROCEDURAL KNOWLEDGE DELAYED POSTTEST. THE RESULTS MAY HELP LANGUAGE TEACHERS DESIGN MORE EFFECTIVE ACTIVITIES FOR THE LEARNERS CONSIDERING THE INSTITUTIONAL CONSTRAINTS. ...