Heat a large skillet over medium-high heat and add the oil. Once the oil is hot, add the sausage links and sear on all sides. Do not cook the sausage all the way through - just brown the outside.
While the sausage is cooking, slice the peppers and onions into strips and place in the bottom of a crockpot.
Pour the marinara, Italian seasoning, red pepper flakes, salt, and pepper over the peppers and onions and stir to combine.
Arrange the sausage links over the top of peppers and onions, pressing them down gently to partially cover them.
Cover the crockpot and cook on high for 3-4 hours or low for 6-8 hours, until the sausage is cooked through and the vegetables are tender.
Remove the sausage and slice into chunks. Return to the crockpot and gently stir to coat everything in the sauce.
Sprinkle with parsley before serving.
Notes
We used Johnsonville Italian sausage which has 3 carbs per sausage link. If using another brand or sausage with a higher carb count, you’ll want to adjust the nutrition information accordingly.It’s not 100% necessary to sear the sausages before cooking, but we like the extra flavor it adds when browning them.Make sure not to cut the onions and peppers too thin as they’ll be cooking for hours in the crockpot and will turn to mush if too thinly sliced.Serve over cauliflower rice or with roasted vegetables.