| 2013 | McLean County Art Center, Bloomington, IL |
| 2012 | Cinema Gallery, Urbana, IL |
| 2011 | Quincy Art Center, Quincy, IL |
| 1983, 1885-86,1988, 1990, 1991, 1993-94, 1995-96 | Richard Gray Gallery, Chicago, Illinois |
| 2000, 2001, 2008 | Gerald Peters Gallery, Santa Fe, New Mexico |
| 2002, 2004, 2005, 2007 | Gerald Peters Gallery, Santa Fe, NM |
| 2002-2004, 2007 | Katharina Rich Perlow Gallery, NY |
| 2006 | Museum, Cedarhurst, Mt. Vernon, IL |
| 1991, 2006, 2009 | Tory Folliard Gallery, Milwaukee, WI |
| 2001 | Hyde Art Gallery, New York, NY |
| 2002 | Quincy College, Quincy, IL |
| 2000 | MB Modern Gallery, New York, NY |
| 1999 | CVA Gallery, College, Illinois State University |
| 1997, 1999 | Elliot Smith Contemporary St. Louis, MO |
| 1995 | Daum Museum of Contemporary Art, Sedalia, MO |
| 1993 | Sherry French Gallery, New York, NY |
| 1992 | Florida Community College, Jacksonville, FL |
| 1977-79, 1981-82, 1984, 1986, 1989, 1991 | Tibor De Nagy Gallery, New York |
| 1989 | Iannetti-Lanzone Gallery, San Francisco |
| 1988 | Evansville Museum of Arts & Science, IN |
| 1987, 1989 | Marvin Seline Gallery, Houston, TX |
| 1974, 1976, 1980-83 | Nancy Lurie Gallery, Chicago, IL |
| 2013 | McLean County Art Center, Bloomington, IL |
| 2006 | Mitchell Museum, Cedarhurst, Mt. Vernon, IL |
| 1987 | Lakeview Museum of Arts and SciencesPeoria, Illinois. Traveled to: Evansville Museum, Indiana, and Bergstrom- Mahler Museum, Neenah, Wisconsin. Video, floor installation, and color catalogue. |
| 1993-94 | Rockford Art Museum.Rockford, Illinois. Catalogue by Gerald Nordland. |
| 2013 | Tory Folliard Gallery, Milwaukee, WI :25th Anniversary Show Tory Folliard Gallery, Milwaukee, WI, Fall Landscape Show |
| 2012 | Gerald Peters Gallery, Santa Fe, NM, Singular Visions Tory Folliard Galler, Milwaukee, WI Watercolor USA, National Watercolor Honor Society, Springfield, MO - prize |
| 2011 | Tory Folliard Gallery, Milwaukee, WI Color Vibrations Show National Watercolor Honor Society, Springfield, MO, Bi-annual Watercolor USA, National Watercolor Honor Society, Springfield, MO -prize Gerald Peters Gallery, Santa Fe, NM Land Use and Misuse |
| 2010 | Tory Folliard Gallery, Milwaukee, WI Watercolor USA, Japan Show, National Art Center, Tokyo |
| 2009 | Tory Folliard Gallery, Milwaukee, WI |
| 2008 | "Icons of the past & Present, Land as Landscape:," Autry National Center, Museum of the American West, Los Angeles, CA |
| 2007 | Group Show, Gerald Peters Gallery, Dallas, TX "Open Lands," Lake Forest, IL Burroughs & Chapin Art Museum, Myrtle Beach, SC |
| 2006 | "Open Lands," Lake Forest, IL |
| 2005 | Group Show, Gerald Peters Gallery, Dallas, TX Tory Folliard Gallery, Milwaukee, WI |
| 2004 | "Lucky Thirteen of Bloomington-Normal, IL, "Mitchell Museum, Cedarhurst, Mt. Vernon, IL "Landscape Show," Tory Folliard Gallery, Milwaukee, WI |
| 2003 | "Open Lands: Landscape," Open Lands Conservatory, Lake Forest, IL "Landscape Show," Tory Folliard Gallery, Milwaukee, WI "Heartlands and Western Vistas," South Texas Institue for the Arts, Corpus Christi, TX "Portfolio of Illinois," traveling show by Western IL University professor Fred Jones, Macomb, IL Wales, UK and various cities in Illinois, such as Springfield, Peoria, Des Plaines, Macomb. |
| 2002 | "Winter Green," Chicago Botanic Gardens, Glencoe, IL "Inspired in Illinois," Lakeview Museum, Peoria,IL "Recent Works by Harold Gregor," Peoria Art Guild, Peoria, IL "New Landscapes," Tory Folliard Gallery, Milwaukee, WI |
| 2001 | "Illinois Landscapes," Wm. Koehnline Gallery, Oakton Community College, Des Plaines, IL "Reflections of the Heartland," Tory Folliard Gallery, Milawukee, WI |
| 1999 | Green Woods and Crystal Waters: The American Landscape Tradition since 1950, The Philbrook Museum of Art, Tulsa, OK; traveling to John and Mabel Ringling Museum of Art, Sarasota, FL; Davenport Museum of Art, Davenport, IA From the ROad, From the River, From the Sky Harold Gregor and Ken Holder, IL, Illinois State University, Normal, IL |
| 1996 | Discovering the landscape of the Americas," Gerald Peters Gallery, Santa Fe, NM; traveling, catalog with introduction by Robert Redford "Plain Pictures; Images of the American Prairie," University of Iowa, traveled to Amon Carter Museum, Ft. Worth, TX Joslyn Museum, Omaha, NE, catalog by Joni Kinsey; Smithsonian Institution, Publishers |
| 1990 | "Harmony and Discord: American Landscape Painting Today," Virginia Museum of Fine Arts Republic of China-USA Australia Watermedia Exhibition, Chung Cheng Gallery, Taiwan |
| 1987 | "In the Country," Bronx Museum, NY, curated by Sigmund Balka |
| 1986 | National Endowment for the Arts, Arts Midwest Regional Exhibition, Minneapolis, MN "Contemporary Midwest Landscapes," Herron Museum of Art, Indianapolis, IN |
| 1981 | "Contemporary American Realism Since 1960," Pennsylvania Academy of Fine Arts, Traveled to Virginia Museum of Fine Arts, Oakland Museum, CA, Holland, Germany. |