Yes, you can install a park bench on grass without a concrete pad underneath. I’ve seen plenty of backyard benches placed directly on lawn, and for light or medium-duty use it can work fine—at least for a while. The catch is that bare grass is soft, uneven, and changes with moisture, so the bench may slowly sink, tilt, or become surrounded by overgrown turf.
If the bench is lightweight—resin, aluminum, or slim wood—and your soil drains well, you can often get away with a very simple setup. But if you want it to stay level and not become a maintenance headache, skip the full concrete pad and try one of these no-concrete footings.
First, use precast pavers or flagstones. Dig a shallow spot for each leg, add an inch or two of compacted stone or sand, and set the paver flush with the grass. This spreads the load and keeps the legs out of wet soil. Second, use screw-in ground anchors. Some benches have anchor holes or can be fitted with auger-style anchors that twist into the ground and hold the legs firmly. Third, create a compacted gravel base. Remove the sod under each leg, fill with crushed stone, and tamp it down. It drains well and resists sinking. Fourth, use a low timber or composite frame as a simple base. This works especially well for wider benches because it spreads the weight across a larger footprint.
The only time I’d strongly recommend concrete is for a heavy commercial-style park bench, a bench placed on a slope, or an area with wet, clay-heavy soil. In those conditions, a small concrete pad or concrete footings below frost line will save you from constant releveling.
For most home and garden benches, the answer is yes: you can absolutely install a park bench on grass without pouring a concrete pad. Just give the legs a stable, dry footing and check it once or twice a season. That way you get the look of a bench sitting naturally on the lawn without the wobble.