Did you give up on mollies, or did MTS get you and now you have Multiple Tank Syndrome?
Oscars are ambush predators that will eat just about anything if they are fed a varied diet. A lot of people only feed them on one food and that isn't the best because they end up with nutritional deficiencies and if you ever run out of that particular food, they go on a hunger strike.
Keep offering pellets (floating and sinking varieties), but remove uneaten food after feeding.
You can try raw or cooked prawn/ shrimp. Remove the head, shell & gut (thin black tube in body) and throw these bits away. Cut the remaining prawn tail into small bit size pieces and offer 1 or 2 bits at a time.
You can buy packets of white bait or blue sardines from fishing tackle stores and even some supermarkets. You can buy other types of fish or seafood too and keep them frozen. Then take a bit out and defrost it, cut it into pieces and offer to fish.
Just be sure to remove any uneaten food after feeding because meat based foods cause ammonia levels to go up really fast.
Most fish will learn to accept new foods over time and it's a matter of offering different foods regularly. When the fish gets hungry, it will eat other things.
Due to the size of these fish, and their meat based diets, you need to do a big water change and gravel clean the substrate every week. If there is too much gunk in the gravel or filter, the fish can develop hole in the head disease or head and lateral line disease. Both of which are caused by a dirty environment and can easily be prevented with regular water changes and tank/ filter cleaning.