In a large skillet, heat the olive oil over medium to medium-high heat. Add the ground beef, cooking until it's almost completely browned (about 5 minutes).
Add the onion, bell peppers, and garlic, & continue to cook until the veggies are tender-crisp (about 3 minutes).
Pour the marinara sauce over top & stir to combine. Add the basil, red pepper flakes, salt, & pepper. Reduce the heat to low, and simmer for about 10 minutes while the flavors combine.
Serve hot alone scooped into bowls, or over spaghetti squash or zoodles. Enjoy!
Notes
I use whatever Whole30 compliant marinara sauce I can find- always looking for added sugar, milk, or soybean oil. You can also make your own!