| Oldenkamp Construction | Ryan Douglas Oldenkamp | — | (805) 460 3122 | GC, remodel, ADU | Paso Robles · San Luis Obispo County | — | — |
| Olivas And Son Painting | Olivas And Son Painting | — | (805) 260 8796 | Windows, patio, painters | Nipomo · San Luis Obispo County | — | — |
| Ollie's Plumbing And Rooter Service | Shane Quist Swinney | — | (714) 592 5253 | Other | Arroyo Grande · San Luis Obispo County | — | — |
| Olsen's Remodel & Construction INC | Ryan Christen Olsen | — | (805) 303 4056 | GC, remodel, ADU | Arroyo Grande · San Luis Obispo County | — | — |
| Omega Marble & Granite | Omega Marble & Granite | — | (805) 440 2648 | Other | Nipomo · San Luis Obispo County | — | — |
| Omega Plumbing Services | Szentmiklosy Shawn | — | (805) 835 8351 | Other | Morro Bay · San Luis Obispo County | — | — |
| On Point Plumbing Heating & Air Conditioning INC | Brian Michael Sturgeon | — | (805) 769 9020 | HVAC | Paso Robles · San Luis Obispo County | — | — |
| On Site Plumbing & Septic | On Site Plumbing & Septic | — | (805) 975 7553 | Other | Atascadero · San Luis Obispo County | — | — |
| One Source Home Solutions | One Source Home Solutions | tim@onesourcehs.com | (805) 548 0110 | Other | San Luis Obispo · San Luis Obispo County | — | — |
| One Time Construction | Joel Cody Mccuistion | — | (818) 693 0820 | GC, remodel, ADU | Paso Robles · San Luis Obispo County | — | — |
| One Touch Environments | Raoul Martin Silva | info@onetouchenvironments.com | (805) 242 2450 | Other | Grover Beach · San Luis Obispo County | — | — |
| One World Construction | Michael Robert Kimbrell | — | (805) 471 5836 | GC, remodel, ADU | Cayucos · San Luis Obispo County | — | — |
| Or Construction Company | Rios Rios Octavio | — | (805) 712 6350 | GC, remodel, ADU | Paso Robles · San Luis Obispo County | — | — |
| Organic Boutique Homes INC | Akos Orosz | — | (805) 250-0251 | GC, remodel, ADU | Atascadero · San Luis Obispo County | — | — |
| Original Electric Co | Original Electric Co | info@originalenergyco.com | (805) 505-5533 | Electricians | San Luis Obispo · San Luis Obispo County | — | — |
| Original Energy Co | Jeffrey James Price | — | (805) 441 3710 | Electricians | Arroyo Grande · San Luis Obispo County | — | — |
| Orlick's Roofing | Michael Paul Orlick | — | (805) 674 1036 | Other roofers | Templeton · San Luis Obispo County | — | — |
| Ormonde Construction LLC | David Eugene Ormonde | — | (805) 423 6467 | GC, remodel, ADU | Atascadero · San Luis Obispo County | — | — |
| Ormonde Excavating | Ormonde Excavating | — | (805) 481 0653 | Other | Arroyo Grande · San Luis Obispo County | — | — |
| Ormonde Truck And Tractor | Ormonde Truck And Tractor | — | (805) 441 6694 | Other | Arroyo Grande · San Luis Obispo County | — | — |
| Orozco Roofing | Anthony M Orozco | — | (805) 266 3940 | Other roofers | Arroyo Grande · San Luis Obispo County | — | — |
| Orozco Roofing INC | Anthony M Orozco | — | (805) 266 3940 | Other roofers | Arroyo Grande · San Luis Obispo County | — | — |
| Ortiz Engineering INC | Ramon Guizar Ortiz | — | (805) 896 9172 | Other | Arroyo Grande · San Luis Obispo County | — | — |
| Osborne Welding & Fabrication | Osborne Welding & Fabrication | — | (805) 610 9923 | Other | Atascadero · San Luis Obispo County | — | — |
| Oscar Visser Construction A Partnership | Stacy Lynn Visser | — | (805) 835 5524 | GC, remodel, ADU | Paso Robles · San Luis Obispo County | — | — |
| Osuna Construction | Noah Marley Garcia | — | (805) 503 0323 | GC, remodel, ADU | Los Osos · San Luis Obispo County | — | — |
| Our Town Construction Remodeling Design | Steven Andrew White | — | (805) 234 3649 | GC, remodel, ADU | Los Osos · San Luis Obispo County | — | — |
| Outback Internet LLC | John Andrew Rees | — | (805) 500 8322 | Other | Templeton · San Luis Obispo County | — | — |
| Overall Plumbing | Overall Plumbing | — | (805) 710 0368 | Other | Arroyo Grande · San Luis Obispo County | — | — |
| P & C Plastering | P & C Plastering | — | (805) 441 2423 | Other | Grover Beach · San Luis Obispo County | — | — |
| P - L Construction | Michael David Peach | — | (805) 550 0774 | GC, remodel, ADU | Templeton · San Luis Obispo County | — | — |
| P A Ruiz Plumbing | P A Ruiz Plumbing | — | (805) 546 8247 | Other | San Luis Obispo · San Luis Obispo County | — | — |
| P D B Groundworks | Eric Ryan Hanson | — | (805) 434 9376 | Other | Templeton · San Luis Obispo County | — | — |
| P W S | Timothy Joel Perozzi | — | (805) 547 8797 | GC, remodel, ADU | San Luis Obispo · San Luis Obispo County | — | — |
| P W S Construction INC | Thomas John Hunter | — | (805) 547 8797 | GC, remodel, ADU | San Luis Obispo · San Luis Obispo County | — | — |
| Pac - West General INC | Eric William Newton | — | (805) 541 1876 | Electricians | San Luis Obispo · San Luis Obispo County | — | — |
| Pace Homes INC | Scott Dean Pace | — | (805) 801 5806 | GC, remodel, ADU | Arroyo Grande · San Luis Obispo County | — | — |
| Pacific Air | Leslie Alean Baier | — | (805) 466 8073 | HVAC | Atascadero · San Luis Obispo County | — | — |
| Pacific Builders | Pacific Builders | — | (916) 383-3168 | GC, remodel, ADU | Grover Beach · San Luis Obispo County | — | — |
| Pacific Builders Of Slo INC | Sean Patrick Bolduan | — | (805) 549 9222 | GC, remodel, ADU | San Luis Obispo · San Luis Obispo County | — | — |