Yes, you can absolutely install an outdoor bench without a concrete pad and bolt it directly into grass. The bench itself does not have to be special; what matters is the anchoring system under it.
A ground screw bench anchor is the most practical option. These are large steel screws that twist into the soil, leaving a flat bracket or plate above the grass. You line up the bench feet with the brackets, drill through the existing holes in the feet, and bolt the bench down with galvanized or stainless hardware. Because the screw threads grip the soil, the bench can feel as solid as one mounted on concrete.
Another option is a no-dig bench anchor or stake anchor. These are heavy-duty metal spikes with a mounting plate on top. You drive them into the ground with a sledgehammer or bar, then bolt the bench to the plates. They work well for garden benches, park benches, and trail seating. Some outdoor benches even come with integrated ground stakes or auger-style legs, so you can skip separate anchors altogether.
If you are bolting down a bench on grass, here is the method I would use. First, check the soil. Dense clay or firm loam holds anchors much better than loose sand or very rocky ground. Mark the four leg positions carefully, then screw or drive the anchors in until only the bracket sits just above the soil. Use a level across the brackets and adjust each anchor height before tightening the bench down. A cordless impact wrench with the right socket makes screw anchors much faster, but a long bar through the eye of the anchor works too.
This no dig bench installation method works well when you choose the right hardware. Go with anchors that are at least 12 to 18 inches long for a standard bench; go longer in soft ground or high-wind areas. Look for galvanized or powder-coated steel so the anchors do not rust under the grass. Leave a small gap between the bottom of the bench feet and the soil so water does not sit against the metal. If the bench has only four small feet, consider adding wide washers or a mounting plate to spread the load.
In short, grass bench anchoring is all about the soil and the anchor depth. You do not need a concrete pad. With the right ground screws or earth anchors, you can bolt a bench directly into grass and still get a stable, long-lasting installation.