Tourism drives Ontario’s economy. Always looking to entice more visitors to the area, it builds its brand through constant marketing initiatives. Aside from tourism, the agriculture and manufacturing industries continue to push Ontario’s growth. Currently, the city is on its way to becoming a center of industrial and business parks. To boost its economy, the city requires assistance from outstanding commercial contractors. In this list, our editors have gathered five leading contractors helping businesses in Ontario.

All these contractors are U.S. Green Building Council (USGBC) affiliates dedicated to creating sustainable buildings. These contractors exhibit a high level of professionalism and excellence in building hotels, corporate offices, schools, and medical centers for Ontario and the surrounding area. 

K.A.R. Construction Inc.

1306 W Brooks Street, Ontario, CA 91762

K.A.R. Construction continues to raise standards in construction quality in California. Serving Southern California, this contractor is USGBC-accredited and California OSHA (Occupational Safety and Health Administration) 30-certified. These accreditations prove the company’s dedication to providing high standards in safe and eco-friendly builds. In addition, it has a LEED-certified (Leadership in Energy and Environmental Design) staff with decades of construction experience. The company holds a General Contracting License (B) and a Concrete Construction License (C-8) as well. 

Established in 1986, this contractor has vast expertise in public works, office, and retail projects. The firm is also an expert in constructing industrial, medical, and school facilities. Based in Ontario, 60% of this family-operated company’s commercial projects are in the city. This number of projects is due to the trust the company has built with its clients over the years. The company has an outstanding reputation for providing quality craftsmanship and timely delivery. For over three decades, K.A.R. Construction has been raising the bar in construction performance. 

Perera Construction

2890 Inland Empire Boulevard, Suite 102, Ontario, CA 91764

Perera Construction’s strength comes from its employee-owners. With empowered employees making decisions, quality in each project is ensured. This employee-ownership approach has created loyalty among key staff and clients and made the company a leader in the business for over three decades. The firm won the 2018 DBIA Merit Award and has been featured in the Engineering News-Record

Working in the healthcare, higher education, and energy sectors, almost half of this contractor’s projects are in Ontario. Founded in 1989, this USGBC-affiliate specializes in complex projects across the west coast. It has licenses in California, Nevada, Utah, and Arizona. Included in its impressive portfolio is the Desert Aurora Medical Center Office Building. This 60,000-square-foot project involved the construction of a two-story medical office with surgical services. In this project, the firm has shown expertise in masonry building, structural steel decking, and the creation of safety building systems. The result is a medical facility that is reliable, sustainable, and durable. 

With over 32 years in the industry, the firm’s range is wide. Among the services it provides are design-build, construction management, engineering, and general construction services. As a company full of employee-owners, the firm provides these services with quality and integrity. 

Fullmer Construction

1725 South Grove Avenue, Ontario, CA 91761

Established in 1946, Fullmer Construction is a construction pioneer in Southern California. Since its opening, it has constructed over 140,000,000 square feet of buildings for several clients. Its projects include industrial and retail facilities, cooler and freezer storage, offices, as well as private campuses and tenant improvements. One of the company’s impressive projects is West Ontario Logistics Center. This 1,196,303-square-foot concrete tilt-up industrial building is situated on 17.17 acres, and located near the I-10, 60, and 91 freeways. This massive building has already been leased out to a high-profile company and includes a speculative tenant improvement of 9,904 square feet of office space and a mezzanine.

Over the decades, Fullmer Construction kept up-to-date with the latest construction trends. It is a USGBC-accredited contractor dedicated to constructing green buildings. With a BBB (Better Business Bureau) A+ accreditation, the company has been providing customer-oriented service for over seven decades. This dedication has earned the company the 2014 Pulse of the City News Star Award. Its popularity has reached different media outfits including the DDC Journal, NAIOP Development Magazine, and Real Estate News Television.

W.E. O’Neil

9485 Haven Avenue, Rancho Cucamonga, CA 91730

Established in 1925, W.E. O’Neil is the longest-running firm on this list. Running for almost a century, it is an award-winning firm and a nationally ranked industry leader. Among its numerous awards is the 2020 AGC Bronze Award for Construction Excellence from the Associated General Contractors. This top contractor has graced multiple magazines including Building Design + Construction Magazine, Engineering News-Record, and Los Angeles Business Journal. On top of that, the firm is a leader in safety and sustainable builds as a USGBC and Cal-OSHA 30-certified firm. 

One of W.E. O’Neil’s outstanding projects is the Cahuilla Hotel and Casino in Anza, California. This project entails the creation of a 32,330-square-foot hotel with a full-service casino. The firm has successfully created an inviting hotel and casino with several areas for relaxation and recreation. Located on an eight-acre site, the firm has also masterfully constructed a parking lot area for the facility. 

Building hotels-casinos is just one of the many projects this top contractor handles. As a century-old firm, it has had decades to hone its expertise in advanced technology, aerospace, and healthcare builds. The firm’s range encompasses the education, infrastructure, and industrial sectors. This outstanding firm serves different areas in the US including Ontario, Los Angeles, Chicago, and Phoenix. 


  • Jake Gustafson

    Jake has served as Senior Editor at General Contractors and brings a wealth of experience rooted in his passion for building. Holding a degree in Construction Engineering Management from Oregon State University, he actively engaged in industry-related activities, including membership in the Associated General Contractors of America student chapter and participation in the Associated Schools in Construction student competition. Previously, Jake served as a project engineer for a prominent general contractor in Portland, where he played a pivotal role in various aspects of construction projects, from pre-construction to subcontractor management. His expertise extends to working on innovative projects, such as North America's largest CLT commercial building. Expertise: Commercial Construction, Commercial Remodeling, Home Design and Build Key Highlights: Editor at General Contractors, Project Engineer for Portland-based general contractor, Field Engineer for the largest CLT commercial building in North America Education: Oregon State University, Degree in Construction Engineering Management