Preheat oven to 450°F and place a pizza stone inside if you have one to heat.
Lightly flour a pizza peel or large baking sheet.
Gently stretch or roll out pizza dough into a 12-inch circle.
In a small bowl, stir together crushed tomatoes, dried oregano, garlic powder, salt, and black pepper.
Transfer dough to the floured peel or baking sheet, drizzle with olive oil, and spread sauce evenly, leaving a ½-inch crust edge.
Sprinkle mozzarella cheese over the sauce.
Arrange sliced bell pepper, sliced mushrooms, and thinly sliced red onion atop the cheese.
Slide pizza onto the hot pizza stone or place baking sheet on oven rack and bake 12–18 minutes, until crust is golden and cheese is bubbly.
Remove pizza from oven, let cool for a few minutes, tear fresh basil leaves over the top, slice, and serve with a green salad.