Among Washington-area organizations offering counseling and special events for single and divorced parents and stepfamilies during the holidays:

* Parents Without Partners. With 1,000 chapters worldwide, it serves divorced, widowed and single parents of all ages, and offers a full schedule of events to help overcome holiday blues. (202) 638-1320.

* Stepfamily Association of America. Its 61 chapters in 28 states include groups in Silver Spring, Md., (301) 598-6229, and Reston, Va., (703) 476-8814. Call for information and publications. The national office is in Baltimore: (30l) 823-7570.

* Separated and Divorced Catholic Support Groups. Offer group support and social activities in Northern Virginia (703) 425-6454, in Montgomery County (301) 948-7545 and in the District (202) 337-2840.

* Fairfax Co. YWCA. Walk-in evening sessions on four consecutive Wednesdays starting this week for single and divorced parents, plus on-going groups in 1985. (703) 560-1111.

* Divorce and Marital Stress Clinic. Rosslyn, Va. Call for appointment. (703) 528-3900.

* Mount Vernon Center for Community Mental Health. Main office in Alexandria and out-patient unit in Springfield offer individual counseling and workshops. (703) 360-6910.

Check listings under Family Services Agencies for specific counseling groups in your area. Family and Child Services of Washington, for instance, offers individual counseling on family-related issues. (202) 289-1510.