OPENQUERY Error when accessing Oracle

It appears that if you want to run the query as written then you don't need to use 4 single quotes around your YYYYMM. You would need them only if the whole statement would be fed into the varchar variable first and then fed into exec so double escaping would be a must. Please try restating your statement like this:

select * from openquery 
(
    OPS_ORACLE_IW, 
    'Select 
        SUM(SLS_QTY), TO_CHAR(SLS_PROC_WRK_DT, ''YYYYMM'') 
        AS SALE_DATE, CNTRC_LEAD_TP_ID, cust_acct_id, EM_ITEM_NUM
        from dcp0.V_SALE_ITEM
        where rownum <=100
        group by    
            TO_CHAR(SLS_PROC_WRK_DT, ''YYYYMM''),
            CNTRC_LEAD_TP_ID,
            cust_acct_id, 
            EM_ITEM_NUM'
);

Oleg