The Mat-Sea-Cal Oral Proficiency Tests are a series of comparable grammatical structure tests. They have been developed in six languages: English, Spanish, Cantonese, Mandarin, Ilokano and Tagalog. Their purpose is to identify linguistic skills and deficiencies of primary school children grades K through 4. This research reported on the psychometric qualities of the English and Spanish editions. Reliability was computed by the method of internal equivalence. Coefficients were .91 on the English test and .94 on the Spanish test. Point biserial coefficients were calculated as the discrimination index. Results varied by subtest (Listening Comprehension, Sentence Repetition, and Structured Response). Factor analysis, via principal factoring with varimax rotation, was employed to identify item pools. Results indicated that approximately 30 percent of all original items require revision. (These tests are labeled "Field Test Edition" by the authors.) The remaining items possessed good to excellent discrimination indices, and difficulty levels appropriate for criterion referenced measures. (Author)