Heat a large (3 1/2 quart) saucepan over medium-high heat.
Once the saucepan is hot, add the oil, onions, bell peppers, and garlic. Cook, stirring occasionally, until onions begin to soften and turn translucent, about 5 minutes.
1 tablespoon olive oil, 1 small onion, ½ medium green bell pepper, ½ medium red bell pepper, 1 tablespoon minced garlic
Add the tomatoes, green beans, salt (if using), and garlic pepper. Bring everything to a boil, then reduce heat to medium-low and cover.
28 ounces fire-roasted whole tomatoes, undrained, 1½ pounds fresh green beans, 1 teaspoon salt, Garlic pepper or freshly ground black pepper
Cook, stirring occasionally, until the tomatoes break down and the green beans are cooked to your liking, about 15 to 25 minutes.