Can this be applied to a deck that was previously stained with an oil based stain a few years ago?

I applied this stain to a old oil stained arbor. I had no problem with coverage and had stood up to rain so far.

Yes, Cabot Solid Color Acrylic Deck Stain can be applied over an older application of Cabot Semi-Transparent Stain providing the deck is cleaned thoroughly and lightly sanded prior to the application. It should also be mentioned that our best recommendation would be to prime first with an exterior oil-based primer followed by two coats of the Cabot Solid Color Acrylic Deck Stain.