Season pork steaks with salt and pepper. Heat oil in a large skillet over medium-high heat and brown steaks for 2 minutes per side in 2 batches; transfer to a 6-quart slow cooker.
Cook onion in the skillet for 5 minutes, add garlic for 30 seconds, then wine and scrape the browned bits. Stir in tomatoes, basil and oregano and pour over the steaks.
Cover and cook on low for 6 to 7 hours until fork-tender and at least 145°F, usually near 190°F for these shoulder steaks.
Lift steaks carefully to a platter and rest for at least 3 minutes. Stir olives and capers into the sauce; if watery, simmer the sauce in a saucepan for 5 to 10 minutes before serving.
Spoon the chunky tomato-olive sauce around each intact steak and serve.