Steam tempeh for 10 minutes (this helps remove the "bitter" taste). Let cool enough to touch, then crumble.
Cook pasta according to package directions. Meanwhile, dice bell pepper, slice mushrooms, and mince garlic.
In a large pan over medium heat, sauté the tempeh, mushrooms, peppers, and garlic for about 8 minutes until veggies soften (add a bit of olive oil to the pan if necessary/desired).
Reduce heat to med-low and pour in pasta sauce. Cook for 10 minutes until heated through, stirring occasionally.
Spoon sauce over cooked pasta. Serve with grapes on the side.