The present study was conducted to investigate the effect of using consciousness-raising tasks, (CR) tasks, on learners' achievement and the quality of their output. The CR tasks were designed by the researcher. The population of the study consisted of students at foundation level at a government college in Muscat. The sample was two contact classes of pre-intermediate level. The total number of the sample was forty seven (47) students; twenty five (25) in the experimental group and twenty two (22) in the control group. Three instruments were used to collect the data; eight (8) designed CR tasks, a grammar test and a dictogloss task. Pre-test was administered to examine the equivalence of the control and experimental group in their grammar knowledge of two targeted grammatical structures (prepositions of time and paired adjectives). Then, the experimental group was given the eight (8) designed CR tasks; four (4) for each grammatical structure, while the control group learned those structures through the Pre-Intermediate Headway textbook. At the end of the treatment, the same test was administered to both groups as a post-test to measure the differences in their achievement. At the end of the course, both groups were asked to complete a dictogloss task to compare the quality of both groups' learning outcomes. The results of the study can be summed up as follows: There was a statistically significant difference between learners' achievement in the experimental and control groups that favored the experimental group, which studied the two grammatical structures through CR tasks. The experimental group learners produced more improved output compared with the control group A number of recommendations for future EFL teaching using Task-Based Learning with specifically focused tasks and dictogloss tasks are presented. In addition, suggestions for further research are proposed.