I truly hope I do not offend you, or upset your sensibilities, but you did ask, so..........

Unlike humans, fish eat only to live and variety isn't important to them, only nutrition. As with any other wild animal that swims, flies, runs or crawls, what "tastes" best to them, and what they consider the best "treat", is what they evolved to eat and once an Oscar is large enough to prey on other other fish, it will do so, because that is what it evolved to eat.

We evolved to eat virtually anything animal and unless downright poisonous; vegetable. Then, we learned to cook, and add other ingredients to basic foods, to make what we ate even tastier to our senses and the more sophisticted our societies and tastebuds became, the more variety we desired in our meals, but our pets don't, and never have.

Brine shrimp are great for baby Oscars, because they replace the tiny inverts and insects it would eat in the wild, but at 7", yours wants grown-up food.

Therefore, the ultimate "home made" food for it or most any large cichlid, is another well nourished, healthy fish it can swallow whole, and why so many cichlid breeders also keep Swordtails and/or Guppies, because breeding their own is safer than buying live feeders.

While adult Oscars primarially eat other fish, as predators, they are also opportunists and given a newborn mouse, (AKA: "Pinkie") will glop it down with relish.

Beef heart, while high in protein, is also deficient in most of the other nutrients your fish would get in the wild by swallowing other fish whole; scales, fins, bones, meat, organs, stomach and gut contents: all produce what the predator fish needs to grow and maintain it's own health, to allow it to sucessfully reproduce, fight off diseases, and escape other, even larger fish.

If you aren't comfortable giving your Oscar it's best natural, live food and it's happy eating cichlid pellets, buy the highest quality brands, keep it sealed between feedings to maintain freshness, and you will keep your Oscar healthier than by offering "variety" in the form of treats that are not it's best, natural food.

It needs TOTAL nutrition, and what is produced by the latest, computer controlled quality production facilities would be difficult if not impossible to reproduce in a home kitchen.

I have had one of my oscars for 14 years, and the other for 9. They are very big, a little too fat, but in very good health. They are both female, but they "breed" (muck up the water with eggs) several times a year.

Why does this matter? Because other than the VERY occasional feeding of live food (perhaps 2x's yearly, tops) they eat nothing but dog food! They LOVE dry puppy kibble, but would probably like the larger kibble just as well, and I bet cat food would be on their favorites list, too.

The only issue I have seen is that the dog food is a little more prone to clouding the water. But with oscars, the filtration system should be VERY efficient anyway...

Kudos to you, for figuring out that it's not the label but the contents of the product that matter.

Puppy kibble is very high in the type of protein a carnivore needs to grow, so your report of using it to feed Oscars rather proves my point about what they need in their diets. Wild puppies, AKA: wolf cubs, are fed the same mix of nutrients, also somewhat pre-digested.